bnwat05 rainwater and greywater - market transformation

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BNWAT05: Rainwater & greywater

systems - Supplementary briefing

note

Version 1.0

This Briefing Note and referenced information is a public consultation document and

will be used to inform Government decisions. The information and analysis forms

part of the Evidence Base created by Defra‟s Market Transformation Programme.

1 Introduction

Rainwater harvesting (RWH) and greywater reuse systems provide non-potable supplies of

water to buildings. By providing an alternative source of water they can help new and

existing buildings reduce demand for mains water supply. These standards may be imposed

by regulatory or local planning requirements. However, the feasibility of these systems in

new and existing buildings must be considered fully prior to development.

The information in this note is for England and Wales as Defra and Welsh Assembly

Government policies and actions may not be applicable in Scotland and Northern Ireland.

The information may be used to inform feasibility studies.

1.1 Purpose of the briefing note

This briefing note defines rainwater harvesting and greywater reuse system technologies

and presents the barriers and opportunities to increased uptake. This note is consistent with

other water sector Market Transformation Programme (MTP) briefing notes by focusing on

domestic households, but also considers the non-household sector. The overall purpose of

this briefing note is to increase uptake of rainwater and greywater systems in situations

where these are technically and financially feasible. It aims to do this by providing the key

facts on both of these technologies: definitions; product types and performance; best

practice installations and yield methodologies; availability and pricing; applicability in

different building types; and future changes in product and policy development.

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1.2 MTP Goals

Sustainable water management is essential to protect the water environment and to meet

current and future demands for water. The key to water efficiency is reducing waste, not

restricting use.

At present, most buildings are supplied with potable water (i.e. wholesome water fit for

drinking) from the public water supply network. Much of this is used in activities where non-

potable water would suffice. For example, in many existing homes, toilet flushing is

estimated to account for around 30 per cent of the household‟s daily demand (although data

from water companies indicates that this average is falling to 26 per cent1 as more new

homes are built to higher standards of water efficiency and older WCs in existing homes are

replaced with lower flush models). In non households toilet flushing may be a much higher

proportion of domestic-type demand.

1.3 Content of the briefing note

This briefing note contains the following information:

Section Information

1: Introduction 1.1 Purpose

1.2 Goals

2: Drivers 2.1 Water availability

2.2 Housing growth

2.3 Building Regulations and the Code for Sustainable Homes

2.4 Surface water management

3: Definitions Definitions and terminology

4: Water use in the home 4.1 How much can be saved

5: Product standards 5.1 BSI Rainwater code of practice

5.2 BSI Greywater code of practice

5.3 Related water regulations

6: Determining feasibility 6.1 Building characteristics

6.2 Economic Factors

6.3 Social Factors

6.4 Opportunities and barriers

7: Sustainability Energy and carbon

8: Innovation Integrated systems

9: Recommendations and action plans

Actions to increase uptake, actions to improve MTP data

Appendix A Product descriptions

Appendix B Environmental benefits

1 BNWAT01 WCs:Market projections and product details

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2 Drivers

2.1 Water Availability

Annual average rainfall in England and Wales varies between less than 700 mm to over

2000 mm per year2. Whilst this is plentiful in some areas (e.g. the north and west of the

country), these rainfall totals have to be put in the context of the demand for water from a

population of approximately 54.8 million3.

The total volume of water that is abstracted every day by the water companies in England

and Wales is 14,449 Ml/d4. Two thirds of this (approximately 75 per cent) is supplied to

households and non households, and the vast majority of this is for domestic use.

However, water is a finite resource and three factors are increasing the pressure upon

existing water resources:

The population is expected to continue growing, particularly in the south-east of

England and there is a trend towards single occupant dwellings. This has been shown

to increase pcc5;

The impact of climate change which UK Climate Projections predicts will reduce

summer rainfall6 and which may at the same time increase climate influenced

demands, such as personal washing; and

Increasing availability of more consumptive water using products such as power

showers, and consumptive behaviours, e.g. increased personal washing. Water

companies‟ Water Resource Management Plans contain strategies specifically aimed

at trying to reduce per capita consumption (pcc). Several water companies have

reported pcc levels that are far above 150 litres per day.

2.2 Housing growth

Significant housing growth is planned for the next 10 to 15 years. The number of households

in England is projected to grow to 27.8 million in 20317, and to a total of 29.2 million in

England and Wales, an increase of 6.3 million (29 per cent) over the 2006 estimate, or

252,000 households per year. This has the potential to increase the demand for potable

water. In particular, development in the south and east will add significant pressure on water

supply in the most water-stressed region of the country.

2 http://www.metoffice.gov.uk/corporate/library/factsheets/factsheet09.pdf

3 http://www.statistics.gov.uk/statbase/Product.asp?vlnk=15106

4 Water UK Water Supply and Infrastructure Data http://www.water.org.uk/home/resources-and-

links/waterfacts/waterindustry/data 5 Herrington (1996). Climate change and the demand for water.

6 UK Climate Projections 2009. Online climate change projections report.

http://ukclimateprojections.defra.gov.uk/content/view/2068/500/ 7 http://www.communities.gov.uk/documents/statistics/pdf/1172133.pdf

http://www.water.org.uk/home/resources-and-

http://www.communities.gov.uk/documents/statistics/pdf/1172133.pdf

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More detail on population and housing growth forecasts is available in BNWAT06: Domestic

water use in new and existing buildings.

2.3 Building Regulations (Part G) and the Code for Sustainable

Homes

The Code for Sustainable Homes and the 2009 amendment to the Building Regulations set

whole building consumption standards for new homes. Part G of Schedule 1 of the Building

Regulations (2000) stipulates that in new dwellings:

“reasonable provision must be made by the installation of fittings and fixed appliances

that use water efficiently for the prevention of undue consumption of water”.

Regulation 17K specifies:

“the potential consumption of wholesome water by persons occupying [the new]

dwelling must not exceed 125 litres per person per day..,[calculated according to the]

Water Efficiency Calculator for New Dwellings”.

The revised Building Regulations are in-line with Level 1/2 of the Code for Sustainable

Homes, with an allowance of five litres per head per day for external use:

Level 1/2 for water is defined as 120 litres/person/day;

Level 3/4 for water is defined as 105 litres/person/day; and

Level 5/6 for water is defined as 80 litres/person/day.

It is generally accepted that achieving level 3/4 of the Code for water can be achieved by

installing an appropriate combination of water efficient fixtures and fittings, and continuing to

influence consumer behaviour. It does not require installation of rainwater or greywater

systems and the cost to deliver a new home to CSH level 3/4 could be approximately £125

per house above the cost of construction of a house to meet the CSH Level 1/2 performance

standard of 120 l/h/d (CLG, 20088). What is important is that achieving CSH level 5/6

standard of 80 litres per head per day (or lower) is likely to require some form of non-potable

water input to domestic properties, e.g. harvested rainwater or reused greywater.

Future developments, particularly in the most water stressed parts of England and Wales,

may require new households to be designed and built to achieve consumption rates at level

5/6 of the Code for Sustainable Homes (80 litres per head per day). This level of water

efficiency is very likely to require some form of rainwater harvesting or greywater reuse. The

nature and design of such systems will depend on wide number of factors, and the success

of these systems will require co-operation from a large number of stakeholders, including

planners, developers, water companies, and others.

8 CLG (2008). Cost Analysis of The Code for Sustainable Homes. Final Report

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2.4 Surface water management

In addition to water resources issues, there are also concerns about rainwater drainage from

urban areas. Planning authorities are required to consider the effects of development on

surface water drainage and the potential impact on flood risk, (Planning Policy Statement

259). The suitability and sustainability of developments will increasingly be judged, in part,

on their requirements for water supply and wastewater removal. Rainwater harvesting has

the potential to provide benefits in the form of attenuating rainfall and minimising surface

water run-off. Further, BRE, which manages the Code on behalf of Communities and Local

Government, has issued guidance that includes consideration of the use of rainwater

harvesting systems to contribute to surface water management, “where infiltration cannot

reduce all of the additional volume [surface water] ….. must evaluate the appropriateness of

rainwater harvesting systems to reduce the residual additional volume by diverting water for

use within the dwelling”10.

Further information on environmental benefits of rainwater harvesting and greywater reuse is

provided in Appendix B.

9 http://www.communities.gov.uk/publications/planningandbuilding/pps25floodrisk

10 BRE (2009). Code for Sustainable Homes – Technical Guidance Note 001 Supplementary

guidance on the assessment of the Management of Surface Water Runoff criteria (SUR 1). http://www.breeam.org/filelibrary/Sur__1__Guidance_note__v12__2_.pdf

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3 Definitions

Wholesome water means water complying with the requirements of regulations made under

Section 67 (standards of wholesomeness) of the Water Industry Act 1991.

Non wholesome water means water that does not meet the requirements for wholesome

water, but is considered suitable for certain applications having regard to the risks to human

health. This could include greywater or harvested rainwater11.

Rainwater is that arising from atmospheric precipitation12.

Rainwater harvesting

The principle of rainwater harvesting is that rainwater is collected from roof areas and/or

areas of hard-standing, treated as appropriate, then pumped, direct or via a header tank, to

or within individual buildings. This water can be used without disinfection for non-potable

applications such as toilet flushing, outside water use, and non-hygiene cleaning. It can be

used for washing machines, although there may be occasional colour and odour issues,

depending on the quality of water collected. A mains supply must be provided for when

there is no rainwater in the storage tank.

Water butts are useful simple systems to provide water for gardens but these are not

included within the MTP definition of a rainwater harvesting system.

Greywater is domestic wastewater excluding wastewater arising from the WC. It is generally

collected from baths, showers and washbasins and may also be collected from kitchen

sinks, although the level of contamination from foodstuffs and other sources usually preclude

the use of kitchen wastewater. After basic treatment, greywater may be used for purposes

around the home such as toilet flushing or garden watering that do not require water of

potable water quality.

Greywater reuse is the use of untreated greywater for purposes that do not require potable

water.

Reclaimed water

Unlike greywater, reclaimed water is that which has not been supplied via the mains, e.g.

untreated borehole water. It is collected and treated for specific non-potable uses such as

flushing WCs.

SuDS

Sustainable drainage measures which alleviate flood risks both at a development site and

elsewhere in the catchment.

11

Building Regulations Part G General Guidance 12

BS 8515: 2009. Rainwater harvesting systems – Code of practice.

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4 Water use in the home

When considering the implementation of alternative supply systems within new buildings it is

important to understand domestic water use patterns. Data on household water use is

available in the water company Water Resource Management Plans. Figure 4.1 represents

the average data from those water companies that have undertaken customer use surveys

and other forms of data collation.

It shows that toilet flushing is the largest single use of water (26 per cent of total demand),

with personal washing (showers, baths and taps) accounting for a further 42 per cent.

Washing machines also account for a significant percentage of the total volume at 10 per

cent. The remaining third is consumed via washing up in kitchen sinks (7 per cent), outdoor

use (9 per cent), and other miscellaneous uses (6 per cent).

As defined in Section 1.2, rainwater is suitable for uses that do not require potable water

quality such as WC flushing and outside use (in total approximately 35 per cent of household

use). Greywater is suitable for WC flushing.

Figure 4.1 Water use in the home

Bath use, 14%

Shower use,

19%

Toilet flushing,

26%

Clothes

washing, 10%

Garden use, 8%

Car washing,

1%

wash basin, 9%

Miscellaneous

use, 6%

Dish washing,

7%

Source: Micro-component data from the water companies 2009 Water Resource Management Plans.

4.1 How much water can be saved

The environmental drivers for saving water and reducing demand for mains supplies are

clear. The question is;

How much water can be saved through rainwater harvesting and greywater reuse?

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On average, each person in England and Wales uses just over 150 litres of mains drinking

quality water every day, so a family of four uses around 220,000 litres per year. In theory, of

this average mains water use, approximately 44 per cent is used for WC flushing, supplying

the washing machine and watering the garden13. This mains water usage could be

substituted with harvested rainwater or treated greywater. There are some concerns over the

use of harvested rainwater for clothes washing mainly that the quality of the water could

damage clothes but these are not prohibitive and may be resolved.

7,599 Ml of potable water is supplied to households in England and Wales each day and up

to one third of this is used to flush toilets. Savings are highly dependent on supply being

sufficient to meet demand and uptake, rainfall patterns, collection systems, and personal

habits (particularly for greywater reuse) will limit the maximum potential from being realised.

However, if just one per cent of all homes used an alternative source of water to flush the

toilet 22.8 Ml/d of water would be saved.

Rainwater can be used to flush toilets and wash clothes if there is sufficient yield and

storage capacity. This is dependent on rainfall and how much of this can be collected and

so savings may vary throughout a year. The installation of a greywater reuse system should

provide more than adequate supply for toilet flushing, and potentially save 20 per cent of

internal household use, in a house already fitted with a highly water efficient WC (e.g. 4.5

litre single flush, or 4/2.6 litre dual flush toilet)14.

4.1.1 Calculating water demand and yield of non-potable technologies

Rainwater harvesting is a simple concept. Rainwater is channelled directly from the

surface(s) it falls on. Once collected and stored it can be used for non-potable purposes.

From a holding tank from the water is fed to the point of use, either by gravity (if the tank is

stored at a level above the point of use), or by a small pump. The volume required is a

function of the demand for non-potable water.

CIRIA15 and the Environment Agency16 have published guidance on how demand and yield

for rainwater harvesting systems should be calculated. The recommended formula is

presented below:

13

Analysis of water company 2009 Water Resource Management Plan micro-component data (survey

based) 14

London Development Agency (2009). Managing Water - Reducing Water Demand. Technical Report (Entec, unpublished).

15 CIRIA (2001) Rainwater and Greywater Use in Buildings: Best Practice Guidance. Report C539. CIRIA, London

16 Environment Agency (2010). Harvesting rainwater for domestic uses: an information guide. Environment Agency. Bristol

Annual rainfall (mm) x effective collection area (m2) x drainage coefficient (%) filter

efficiency (%) x 0.05

(Environment Agency (2010). Harvesting rainwater for domestic uses: an information guide).

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This calculation takes account of:

Annual rainfall totals and the temporal variation in rainfall in the specific site location;

The effective collection area (m2) (equal to the area of roof and/or hard-standing that

can be reasonably used to collect rainfall);

A drainage coefficient (based on type of roof and other catchment materials, and the

proportion of actual rainfall that can be collected, allowing for surface wetting,

evaporation and excess runoff during intense storm events); and

Filter efficiency; of the water that is collected in the gutters not all will reach the

holding tank. (manufacturers usually advise that 90% of the water flowing into the

filter is retained).

The feasibility of greywater systems is independent of rainfall and less likely to be affected

by occupancy rate. However, it could be that occupants of a single in-house system use

only a small amount of water for bathing and spend the majority of the day at home,

therefore using a larger amount of water for flushing the toilet. This would create a higher

demand for treated greywater than the quantity available and would also lead to minimal

water savings.

Unlike rainwater systems which are heavily dependent on the dimensions of a building to

generate sufficient yield, and in general the feasibility of greywater is affected more by the

performance and perception of the technology. The following formula calculates the demand

and the yield of greywater systems:

Feasibility assessments also need to consider the energy impacts of moving water around a

property for reuse.

4.1.2 Current Ownership

Around 2000 rainwater harvesting systems were installed in the UK in 2006/0717 and by

2010 this is believed to have increased (there are no data for England and Wales

specifically). Of these, 70 per cent were domestic systems18. The majority (> 95 per cent)

17

Environment Agency (2008). Harvesting rainwater for domestic uses: an information guide. Environment Agency. Bristol

18 Email communication, Rainwater Harvesting Association (October 2010).

Demand = per person daily average WC flush x occupants sharing greywater system

A second formula calculates the daily non potable supply (i.e. water from bath/shower)

Supply = per person personal washing demand* x occupants sharing greywater system

*Taken from the CSH Water Use Calculator

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are sold for installation in new buildings. Retrofit rates are currently quite low since there are

few incentives to counteract the installation costs that are often prohibitive in existing

buildings. There may be some incentive from savings on water bills but these will only apply

to metered customers and may be limited due to the current low price per unit of water. One

of the main issues limiting retrofits is the physical constraint of accommodating a water

storage tank.

There has been a recent shift (2008-2010) in the types of developers who procure rainwater

harvesting systems from mainly self-builders and small developers to social housing

contractors and major developers in the UK19. This may demonstrate that rainwater

harvesting is moving from the small-scale peripheral market to more mainstream

developments. Social housing is a development sector that offers large scale potential for

improving water efficiency. The Code for Sustainable Homes was developed using the

Building Research Establishment‟s (BRE) EcoHomes System, which had already achieved

success in reducing the impact of affordable housing projects, in particular within the social

housing sector20. Waterwise has also made recommendations for the Government to

include water efficiency in the Decent Homes initiative, particularly by recommending water

efficient showers as a standard fitting21. The Code for Sustainable Homes now requires new

social housing developments to meet level 3/4 for water.

19

Email communication (October 2010): SCP Environmental Ltd 20

CLG (2006). Code for Sustainable Homes . A step-change in sustainable home building practice. http://www.planningportal.gov.uk/uploads/code_for_sust_homes.pdf 21

Waterwise (2009). Beyond Decent Homes. Memorandum. http://www.publications.parliament.uk

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5 Product standards

An increase in the market for rainwater systems has led to Codes of Practice being

developed for rainwater and greywater systems. These standards are designed to ensure

that recycled water does not pose a risk to human health and have been produced in

response to the expansion in the rainwater harvesting and greywater reuse sector.

5.1 BSI Rainwater code of practice

BS 8515:2009 was published and came into effect on 31 January 2009. It sets out

recommendations on the design, installation, testing and maintenance of rainwater

harvesting systems supplying non-potable water in the UK. It covers systems supplying

water for domestic water uses (in residential, commercial, industrial or public premises) that

do not require potable water quality such as laundry, WC flushing and garden watering. It

does not cover systems supplying water for drinking, food preparation and cooking,

dishwashing and personal hygiene. A rainwater harvesting system with filtration conforming

to Section 4.3 of the standard will provide water of a suitable quality for WC flushing, laundry

and garden watering in most residential, commercial and industrial situations. However,

where greater human exposure to the water is anticipated or where the water is to be used

in public premises, this could require higher water quality. In such cases, the system may

incorporate treatment processes such as ultraviolet (UV) or chemical disinfection22.

5.2 BSI Greywater systems code of practice

The British Standard for greywater systems is divided into two parts. Part 1, BS 8525-

1:2010 Greywater Systems: Code of Practice came into effect on 30 June 2010. As a code

of practice, this first part of BS 8525 takes the form of guidance and recommendations. It

does not specify compliance requirements. Part 2, Part 2: Domestic greywater treatment

equipment – Requirements and test methods, will provide more detail on the specification of

treatment equipment and the procedures for testing system performance.

Part 1 of BS 8525 gives recommendations on the design, installation, alteration, testing and

maintenance of greywater systems utilising bathroom greywater to supply non-potable water

in the UK. It covers systems supplying water for domestic water uses (in residential,

commercial, industrial or public premises) that do not require potable water quality such as

laundry, WC and urinal flushing and garden watering. It also covers individual and

communal systems; and it applies to retrofitting and new build. It does not cover systems

supplying water for drinking, food preparation and cooking, dishwashing and personal

hygiene; direct reuse systems for external use; product design for specific system

components; or the reuse of trade effluent.

22

BS 8515:2009 Rainwater harvesting systems –Code of practice [Section 4.3]

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5.3 Related water regulations

Water Supply (Water Fittings) Regulations 1999 in England and Wales.

If a rainwater harvesting system is inadequately installed, it could become a public

health hazard. Of specific concern is accidental contamination of mains water with

rainwater. The Water Supply (Water Fittings) Regulations 1999 aim to prevent this.

The main safeguard that the legislation requires is that a type AA air gap must be used

at the point where the mains top-up enters a rainwater harvesting system. A type AA

air gap ensures that there is a physical separation between the two types of water,

ensuring that no rainwater can be drawn back into the mains water supply23. The

Regulations also require appropriate marking of pipes that contain non-potable water.

WRAS Information and Guidance note 9-02-05 states that:

- It is important that all pipe-work supplying reused water is readily identifiable to

those who come across it for the first time;

- Pipe-work should be both recognisable and distinguishable from that supplying

mains water; and

- Pipes must be marked and labelled.

Building Regulations Part G. Part G24 covers sanitation and water efficiency, defines

wholesome and non wholesome water, it confirms that to be considered wholesome,

water must comply with the requirements of Section 67 of the Water Industry Act 1991,

and that the relevant regulations under this are:

- The Private Water Supplies Regulations 1991;

- The Water Supply (Water Quality) Regulations 2000 (SI 2000/3184) for

England; and

- The Water Supply (Water Quality) Regulations 2001 (SI 2001/3911) for Wales.

Building Regulations Part H. Part H covers drainage and waste disposal. The

regulations are that rainwater or greywater tanks should prevent leaks, have an anti-

backflow device, and be accessible for cleaning. The regulations also set out the

requirements regarding correct labelling of pipe-works and other measures to prevent

cross-contamination of water within the building.

Part H states that further guidance on systems for greywater and rainwater re-use can

be found in the Water Regulations Advisory Scheme (WRAS) leaflet number 09-02-04,

23

Environment Agency (2008). Harvesting rainwater for domestic uses: an information guide.

Environment Agency. Bristol 24

Building Regulations Part G General Guidance

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Reclaimed Water Systems. Information about installing, modifying or maintaining

reclaimed water systems25.

As the market for rainwater and greywater systems is increasing, so too are the number of

manufacturers and the range of products that are available. Several sets of standards have

been developed in order to provide purchasers with guidance on the water efficiency of the

whole range of water using devices, and many of these include efficiency and/or

performance criteria for rainwater and greywater system products. These standards

distinguish between products in terms of water consumption/efficiency performance and

include:

The Water Technology List (WTL)26 (which underpins the Enhanced Capital Allowance

(ECA) scheme developed by the Department for Environment, Food and Rural Affairs

(Defra) and HM Revenue and Customs (HMRC). A qualifying rainwater harvester must

include: a storage level monitor; mains back up control unit; and a filter and storage

tank. A greywater system must enable recovery and on-site reuse of ≥ 40% of the

wastewater received by system;

The Bathroom Manufacturer‟s Association (BMA) Water Efficient Product Labelling

Scheme.27 The scheme provides access to a database of bathroom products which

when installed and used correctly will use less water, save energy and save money.

Currently only one greywater system is included in the BMA labelling scheme;

The Association of Environmentally Conscious Builders (AECB) develops & publishes

standards for sustainable building28. The AECB standards state that rainwater and

greywater systems are generally not recommended, but may be suitable for installation

under certain circumstances.

25

Published in 1999. January 2011 this is still a live document on the WRAS website:

www.wras.co.uk [publications] 26

www.eca-water.gov.uk 27

www.water-efficiencylabel.org.uk 28

www.aecb.net

http://www.wras.co.uk/

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6 Determining the feasibility of a non-potable supply

This section sets out the key factors that should be considered when determining whether a

non-potable supply system would be feasible in a property and the specific factors to

determine whether a rainwater or greywater option is most suitable.

The technical and economic feasibility of a system is based on:

The household/property demand for non-potable water;

The supply yield (i.e. rainfall for rainwater harvesting, or used potable water for

greywater reuse);

Demand and yield are heavily dependent on the type of building/development (building

dimensions, expected occupancy, types of water use);

Cost of technology (including installation), payback period, and maintenance costs.

The influence of cost factors on the decision to install a non-potable system is directly

related to the „ownership‟ factor, i.e. who will bear the costs, who will be required to

fund and manage maintenance, and who will benefit from the longer term payback;

The level of investment cost is affected by when non-potable options are considered in

the planning, design and development process, i.e. costs can be reduced or mitigated

when a system is integrated into a development at the planning and design stage.

There also other social factors that influence uptake of these technologies. Perceptions

regarding the reliability and quality of the non-potable water, health and safety concerns, and

attitudes towards householder maintenance of the water supply systems, all contribute to

user uptake and the effectiveness of non-potable water systems.

6.1 Building characteristics that affect demand and yield

The feasibility of rainwater harvesting and greywater reuse varies depending on the nature

of the development. Key factors include the overall nature of the building (e.g. high rise flats

compared to large detached houses), the density of residential units, the expected

occupancy rate, and the space available within a building and property (including garden) for

tanks, treatment, plumbing and control systems. A London Development Agency (LDA)

study29 considered six generic development types to examine the feasibility of these

technologies; three types of flat development, and three types of house developments. The

key defining characteristics are summarised below and the low water technologies that may

be applicable to each is presented in Table 6.1.

29

London Development Agency (2009). Managing Water - Reducing Water Demand. Technical

Report (Entec, unpublished).

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The results (based on typical rainfall in London) suggested that rainwater harvesting is most

suitable to properties with a low ratio of expected occupants to roof catchment, i.e. low

density housing units with a large roof area.

Such developments are most commonly low rise apartment blocks or moderate to large

houses. In these situations, a communal system (up to five properties) may be more cost

effective in terms of tank size and yield.

Table 6.1 Summary of non-potable technology suitable for different household

building types.

Water

Efficiency

Measure

Luxury

High Rise

City Flats

Standard

Mid Rise

Flats

Low Rise

Flats

Small

Houses

Medium

Houses

Large

Houses

Rainwater

(toilet

flushing)

Possibly with

ratio of 1

resident: 25m2

roof

catchment.

Alternatively

use water

butts for

landscaping

Possible if occupant density

is 1:26m2 or less (most likely

if development includes large

surface area of mixed use

development to increase

yield).

Yes with 700-

800 litre storage.

However,

communal

system (5

houses) offers

better value for

money.

Yes. Reliability when using

for flushing and clothes

washing maybe less than for

toilet flushing only but the

overall savings make this a

feasible option for housing

types with occupant:

catchment ratios of 1:25m2+.

Storage tank between 800 to

1300 litres.

Rainwater

(toilet flushing

and washing

machine)

No No No

Greywater Yes. 100 litre storage is sufficient. Space is a

constraint. Careful planning at design stage is

essential.

Yes. 100 litre storage is sufficient. Less compact

(cheaper) systems may be acceptable as long as

included at design stage. Not in addition to

rainwater harvesting system (not cost effective).

In practice, most household roof areas are too small to satisfy all the potential demand for

rainwater, at all times of the year, regardless of practical storage tank capacity. It is therefore

important that the potential savings are fully evaluated before investing in an expensive

installation. In existing homes, it is generally more economic to reduce water use by fitting

more water efficient appliances and adopting water efficient behaviours before considering

the use of either rainwater (except a waterbutt) or greywater.

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6.2 Economic factors influencing uptake of non-potable

technologies

6.2.1 Capital expense

A key element that must be considered in the context of market transformation is product

pricing. If a product has a price premium associated with it then this is likely to negatively

impact on uptake. Rainwater harvesting companies have stated that the capital cost of

rainwater systems for retrofitting are generally considered very expensive and are not

appealing in terms of simple payback periods for a typical household. The companies go on

to report that if the house is being extended or extensively refurbished then it may be

possible to install a system and the cost is not much more than a system in a new build.

At present, water is relatively inexpensive in England and Wales, typically around 94 pence

per cubic metre (p/m3, with one cubic metre equal to 1,000 litres) for water delivered, and

119p/m3 for sewage collected30. The installation of an alternative domestic water supply is

quite costly, with an initial outlay of around £1,000 - £1,500 for a basic above ground

domestic system (2,600-3,600 litres storage)31. A wide range of costs are quoted by

rainwater harvesting companies, reflecting the different installations, with typical costs in the

region of £400 to £3450 per house at year 2000 prices32.

In addition to the cost of the equipment, there is also the cost of installation and maintenance

to consider. A rainwater harvesting system will require labour and excavation equipment to

install the storage tank and all the systems will require a trained plumber to install the

ancillary components and distribution pipe-work. An Environment Agency study reports that

the plumbing and fitting costs of installation can be around £1,00033.

However, rainwater harvesting companies have reported that the “costs for buying and

installing a system have decreased as the demand has increased. The largest reductions in

cost are available to sites in which multiple systems are required, such as social housing”34.

For larger commercial tanks of up to 100,000 litre capacity, tanks costs approximately

£10,000. Large scale housing developments with shared maintenance and infrastructure

are more likely to make systems financially attractive to install because of economies of

scale. Maintenance and operation costs listed as being typically in the order of £50-£160

30

http://www.ofwat.gov.uk/legacy/aptrix/ofwat/publish.nsf/Content/rpt_int_08unitcostswater.html [Table 6]

31 www.rainwaterharvesting.co.uk

32 Environment Agency (2008). Water related infrastructure for sustainable communities: Technological Options and Scenarios for Infrastructure Systems. Science project SC050025. Environment Agency. Bristol

33 Environment Agency (2010). Harvesting rainwater for domestic uses: an information guide. Environment Agency. Bristol

34 Email communications (October 2010). SCP Environmental Ltd

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per year35. This can be reduced if householders are able to carry out some simple tasks

themselves such as:

Cleaning filters approximately three times a year, depending on tree cover over the

collection area;

Keeping gutters free of debris to prevent blocking the system; and

Visually inspecting the outside of the tanks for leaks etc at least once a year.

BS 8515 recommends checks once per year but these maintenance tasks may need to be

done more regularly as required.

However there are some elements of the maintenance that the householder will not be able

to carry out and where costs will be incurred. Entry into rainwater tanks should be avoided

unless absolutely necessary, and should only be attempted by a trained professional who

has the appropriate equipment and training to work in confined spaces.

The maintenance and repair of communal systems is a more ambiguous area. The topic

has been considered by the Construction Industry Research & Information Association

(CIRIA). The CIRIA report, Rainwater and Greywater Use in Buildings: Project Results From

The Buildings That Save Water Project; Best Practice Guidance36, provides advice on the

use and development of model operation and maintenance arrangements for both rainwater

and greywater systems. It also includes simple guidance on how to incorporate these

systems in developments.

Certain sectors of the market have seen prices for rainwater and greywater systems fall. The

single house system price has begun to fall in the past couple of years, driven by a few

factors: there are less well engineered systems being sold at a lower price to the larger

purchasers; there are many more suppliers in the market than there were, and this ultimately

drives prices down as the market becomes more competitive; and economies of scale also

assist in reducing prices37. The price of greywater reuse systems is likely to be negotiable

based on the number of units required and manufacturers keen to enter the new build

market.

Commercial developments can take advantage of the Government‟s Enhanced Capital

Allowance Scheme. Rainwater and greywater system products and components are

35

Environment Agency (2008). Water related infrastructure for sustainable communities: Technological Options and Scenarios for Infrastructure Systems. Science project SC050025. Environment Agency. Bristol

36 CIRIA (2001). Rainwater and Greywater Use in Buildings: best practice guidance (C539),

London.

37 Email communications (October 2010). Rainwater Harvesting Association

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included on the Water Technology List38 and so capital allowances can be claimed on these

as well as for more standard water using fixtures and fittings.

6.2.2 Operating expense

Once in place, household rainwater systems will require investment to maintain operation.

Ongoing maintenance costs are estimated at around £50 per year, and pump replacement

will be required approximately once every ten years at a cost of around £200.

Over a 30-year accounting period the capital and operating costs have an estimated present

value of £2,300 and £930 respectively39. Inclusion of a rainwater system would not add

significantly to the costs of domestic electricity bills due to the relatively low energy

requirements for operating the pump (0.6kWh/m3). Entec has previously40 calculated the

present value of the additional annual energy cost required to run a rainwater system is £10

over a 30-year period using current prices.

Only customers with water meters will benefit financially from using a non-potable water

supply system. By October 2010 this applied to approximately 37 per cent of domestic

properties and almost all industrial and commercial customers. Therefore, in England and

Wales, for the majority of domestic customers, there is no financial incentive to install a non-

potable water supply system41. Suppliers of rainwater harvesting systems currently claim

savings of over 14 per cent of water used by the average household, but this still gives

payback periods well in excess of 10 years, based on the current unit cost of water and

wastewater services for domestic customers.

The financial situation is different for non-domestic premises as these are generally all

metered and the savings achieved, by rainwater harvesting systems in particular, will be

greater in larger buildings (such as industrial units and schools) due to their larger roof areas

and potentially greater demand.

Discussion with manufacturers has indicated that the non-household, new build, market has

increased quite significantly in the last few years. As that market has grown, the

technologies have improved, awareness has increased, and the costs have started to fall.

All of these factors may help to stimulate growth for rainwater and greywater systems in the

household market.

39 London Development Agency (2009). Managing Water - Reducing Water Demand. Technical Report (Entec, unpublished).



41 Environment Agency (2010). Harvesting rainwater for domestic uses: an information guide

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6.3 Social factors influencing uptake of non-potable technologies

Studies by the Consumer Council for Water42 and the Environment Agency43 have shown

that few people think about their water services in the course of their everyday lives, and of

those that do, many underestimate the volume of water used in typical household tasks.

This presents a serious challenge to efforts to reduce demand, particularly for those wanting

to encourage the adoption of water efficiency measures within the wider consumer base (for

example, through retrofitting), but also highlights the opportunity and importance of building

low water use technologies into new developments. Water reuse technologies must meet

consumer expectations to deter users from reverting to 100 per cent supply from potable

mains supplies.

At present rainwater and greywater systems are not common in England and Wales. This

may be because:

Systems are expensive to purchase, maintain and run, while the cost of water is

relatively low;

Only 37 per cent of domestic customers have metered water supplies and thus would

save money;

Concerns that the quality of the water (particularly greywater) may pose a risk to

health. However, in 2007 the MTP carried out a review of rainwater and greywater

systems and made recommendations for quality guidelines and monitoring

arrangements44. The British Standards subsequently published guidance and

recommendations within BS 8515:2009 Rainwater Harvesting Systems: Code of

Practice, and BS 8525-1:2010 Greywater Systems Part 1: Code of Practice. These

standards are designed to ensure that reused water does not pose a risk to human

health; and

The reliability of greywater systems has been poor in the past and remains largely

unproven in terms of a mass market. It should be noted that rainwater harvesting

systems have also had a lot of reliability issues.

The health concerns are twofold: firstly, the health risk from contact with harvested or reused

water in the normal operation of the system and, secondly, the health risk posed by the

failure or ineffective operation of the treatment system. Greywater reuse systems are

designed to ensure that there is minimal user contact with the greywater. Aerosols from toilet

flushing are the only potential contact most users will have with the water and this is unlikely

to have health implications providing the manufacturer‟s maintenance procedures are

followed and the water has been properly treated.

42

Consumer Council for Water (2006) Using Water Wisely. 43

Environment Agency (2007e). Towards Water Neutrality in the Thames Gateway. Public acceptability of water efficiency scenarios. Science report: SC060100/SR2. Environment Agency. Bristol

44 Market Transformation Programme (MTP), Rainwater and Grey Water: Review of water quality standards and recommendations for the UK, www.mtprog.com

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6.4 Opportunities for, and barriers, to the incorporation of

rainwater and greywater

6.4.1 Developers

The large scale housing development forecast by the Government45 creates an opportunity

to increase the number of households incorporating non-potable water supply systems. In

new developments, it may be possible to incorporate communal systems into large-scale

housing developments thus bringing economies of scale to the installation, performance and

maintenance of the systems. Such communal systems may include additional storage

capacity to provide stormwater control as part of a Sustainable drainage system (SUDS).

For larger scale systems, i.e. where greywater is discharged from households, the water

may be treated in the same way as sewerage using traditional biological methods combined

with modern filtration methods. Such a system may be combined with a sustainable

drainage system as a concept at a building‟s design stage rather than post construction

retrofit. The economy in both the reduction of water and sewerage charges may tip the

financial balance in favour of such a system.

The construction of high density mixed-use developments may limit the roof space available

per person to capture rainwater, whilst there may be insufficient rainfall to ensure that the

systems operate economically. Greywater systems do not have the same resource

limitations as rainwater systems since significant volumes of greywater will be generated.

The following information draws on previous work published by the Watersave network46 and

a recent feasibility study undertaken by the London Development Agency47. Table 6.2

highlights the opportunities and barriers to greywater reuse in new developments, rather

than existing homes. For example, the high capital costs to purchase the systems may deter

residents of existing properties from installing this technology. It should also be noted that

different stakeholders have different priorities regarding the opportunities and barriers

identified in Table 6.2.

45

http://www.communities.gov.uk/documents/statistics/pdf/1172133.pdf 46

Roaf, S. and Ghosh, S. (2002) Barriers and Drivers to Water Conservation and Recycling. Presentation to the Watersave Network. Presentation available from http://www.watersave.uk.net/Presentations/index.html and Baynes, S. (2002) Barriers to greywater recycling. Presentation to the Watersave Network. Presentation available from http://www.watersave.uk.net/Presentations/index.html.


http://www.communities.gov.uk/documents/statistics/pdf/1172133.pdf

http://www.watersave.uk.net/Presentations/index.html

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Table 6.2 Opportunities and barriers to the incorporation of rainwater and greywater

into new developments

Category Opportunities Barriers

Physical Significant volumes of greywater will be

generated in new developments.

New developments allow systems to be

designed into the development at the build

stages.

Mixed use developments present

opportunities for domestic greywater to be

used in adjacent commercial or industrial

applications. Rainwater could be collected

from commercial roof space and used in

adjacent residential developments.

Space required for storage tanks may not be

available.

Roof area may be insufficient to generate sufficient

rain water to meet demand.

Rainfall availability in the London region.

Potential conflict with other policies, such as green

roofs.

Performance Performance of systems is improving based

on experiences of trial developments.

Opportunity to incorporate experience from

other countries to influence design and

system.

System reliability issues with greywater systems.

Maintenance requirements.

Economic Reduced water bills for the customer.

Economies of scale for rainwater and

greywater systems being introduced into

large developments at the communal scale.

Ongoing maintenance costs.

Requirements for a contractor to maintain the

systems.

Social - Unfamiliar technology.

Impact on lifestyle.

Requires commitment from householder to ensure

that system operates correctly.

Perception Opportunity to capitalise on the consumer‟s

“environmental stewardship”.

Homes meeting high standards of

environmental performance seen as “trendy”.

Recent drought events have highlighted water

scarcity as an issue.

Refusal or disgust at the concept of re-using water

used by other people.

Lack of perception of need for this technology amongst

the public.

Water seen as less important than other environmental

objectives such as energy use.

Legislation Level 5 and 6 of the CSH may require reuse or

harvesting technology.

No clear standards determined for water quality in

greywater and rainwater systems.

Environmental Potential to benefit other environmental

measures such as flood risk mitigation.

Reduction in mains water demand.

More concentrated sewage being returned to sewers.

Greater use of disinfectants in greywater systems.

Embodied energy and carbon within the product

materials (e.g. storage tanks), and operational use.

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6.4.2 Existing housing

Existing householders do not have the same drivers or opportunities as developers. An

existing home is not subject to the water efficiency standards set out in the Building

Regulations, and an existing homeowner is unlikely to benefit from retrofitting their home to

adhere to the Code for Sustainable Homes. They may reduce their energy and water bills

but compared to the capital cost of the system and taking account of the additional power

demands that may be associated with a non potable system, these savings are likely to be

small. This is especially true for water whilst the unit price of water is still relatively cheap.

The financial payback period for an existing homeowner may therefore be lengthy.

Similarly, an existing homeowner will not have the buying power and economy of scale that

developers have. Installing non-potable systems into existing household is a retrofit process.

The cost of design and labour is higher than in a new build, and perceptions of prohibitive

costs may deter potential homeowners. The financial savings that could be accrued for a

customer on a metered supply are currently much less than the cost of installing and

maintaining non-potable water supply technologies. Currently, the main driver for existing

houses is a desire to be „green‟ or a desire to pioneer a new technology.

While it is possible to introduce rainwater and/or greywater systems into existing buildings,

consideration at the planning stage can improve their effectiveness, make installation more

straightforward and reduce cost.

6.4.3 Non-domestic premises

The situation is different for non-domestic premises as these are generally all metered and

the savings achieved, by rainwater harvesting systems in particular, should be greater in

larger buildings (such as industrial units and schools) due to their larger roof areas and

potentially greater demand.

In non-domestic premises, rainwater may be used in many other areas of application as a

substitute for mains water (e.g. cleaning, process water, irrigation and humidification, fire–

fighting, toilet flushing etc). In addition, reclaimed water might be reused along with

rainwater in industrial applications (e.g. for cooling water, filter backwash water and some

process water).

Manufacturers have also reported that the need to comply with BREEAM has seen the

commercial market grow and has seen the inclusion of rainwater harvesting in large

numbers of new public type buildings (e.g. schools, colleges, prisons, health centres, and

fire stations)48.

48

Email communication (October 2010): Aquality Trading & Consulting Ltd.

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7 Sustainability of non-potable technologies

7.1 Energy and carbon

Water efficiency is seen as part of the solution to the increasing pressure on the water

environment, from growing population, increased demand, climate change, and increasingly

stringent environmental legislation seeking to reduce water abstraction in areas where

abstraction is causing environmental degradation. However, whilst water efficiency can be

seen as a positive step it may clash with other sustainability issues and environmental

considerations, most notably on carbon.

The Environment Agency greywater information guide49 shows that supplying a low flush

toilet with greywater requires approximately seven times the energy that is required when

using mains water. Embodied carbon within the materials used to manufacture and install

greywater and rainwater systems can be considerable, i.e. fibreglass/plastic tanks, and

concrete bases. The embodied carbon from infrastructure elements of rainwater systems

could be as much as 36 per cent of the total carbon dioxide equivalent impact of the system

over a 30 year lifespan50.

The carbon emissions that result from using a typical RWH system are, on average, around

40 per cent greater than emissions from using mains water. The evidence shows that

collecting, storing and pumping rainwater for domestic uses is not an energy saving

technology.

Over a 30-year lifetime the net emissions split of operational and embodied energy varies

considerably. Research shows that for an average 90m2 semi-detached house with 3

occupants the split is 52 per cent operational to 48 per cent embodied emissions, excluding

emissions from excavation and transport. This highlights that the carbon contribution from

embodied and operational emissions of a RWH system are both significant parts of a

system‟s total emissions.

Although rainwater and greywater systems do introduce additional energy demands for

pumping and treatment, it‟s important to put these emissions in context. The amount of

energy used by even the most complex reuse system is small compared with the energy

used to heat water in the home. Heating water for domestic uses, such as showering and

bathing currently contributes about five per cent of the UK‟s annual greenhouse gas

emissions51.

49

Environment Agency (2008c). Greywater: an information guide. Environment Agency. Bristol 50

Thornton. J. (2008) Rainwater harvesting systems – are they a green solution. In Green Building Magazine, Spring 2008 pp 32-35

51 BNWAT07: Water and Energy Use.

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8 Non-Potable Technology Innovation

Recent years have seen increased interest in „green‟ technologies and greywater reuse is no

exception52. Rainwater harvesting is on the increase in the UK and the UK Rainwater

Harvesting Association formed in 2004 in response to this. The Association now has 31 full

members, who are all UK companies. Research undertaken by Entec for the MTP update

included consultation with the Rainwater Harvesting Association and several specific

companies. It concluded that in the last three to five years there has been growth in the

number of companies providing these services, a direct response to the increase in demand.

Whilst some manufacturers have spent time developing more efficient products over the last

five years (since 2005), many of the systems available on the market have not changed. The

British Standard has seen a standardisation of design and components and, coupled with

BREEAM, has ensured that system sizes are, in the main, fit for the intended purpose53.

Use of rainwater harvesting is increasing in Japan, Australia and Germany, and is more

widespread in these countries than in England and Wales. In Japan planning regulations

require that buildings with a floor area greater than 30,000m2 have rainwater harvesting

installed, while in Belgium buildings with roof area greater than 100 m2 are required to have

combined rainwater harvesting and stormwater attenuation systems. In Germany around

1.5 million homes and workplaces have rainwater systems installed54.

Similarly, greywater reuse systems are not as common in England and Wales as they are in

some other countries. One drawback to greywater reuse is the potential for health

implications if systems prove unreliable. Other countries are dealing with this in different

ways. For example in Japan, only washbasin water is used to flush household toilets. On a

wider scale however, the Japanese reclaim wastewater to flush toilets, for irrigation, and for

use in ornamental ponds/fountains. This happens in high rise buildings and at regional

treatment plants. The processes are sophisticated and expensive but because of Japan‟s

severe water shortage, it is economical55.

Specific regulations and requirements for treating and using greywater vary between

countries and states. However, countries with severe water shortages have identified the

best technical approach for them and encouraged uptake through incentive programmes.

For example, the Australian Government offers A$500 rebates for the installation of a

greywater system. Several municipalities of Spain, including Sant Cugat Del Vallès near

Barcelona and several other municipalities in Catalonia, have also passed regulations to

52

Environment Agency (2008). Greywater: an information guide. 53

Email communication (October 2010). 54

Environment Agency (2010). Harvesting rainwater for domestic uses: an information guide. Environment Agency. Bristol

55 Australian Water Research Foundation. Domestic Greywater Reuse: Overseas Practice and its

Applicability to Australia. http://www.fwr.org/wsaa/wsaa73.htm

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promote greywater reuse in multi-storey buildings56. Other countries also have incentive

programs for installation of greywater systems, including Korea and Cyprus57.

8.1 Integrated rainwater and greywater systems

Integrated systems include both rainwater harvesting and greywater reuse systems. Factors

that influence the success of such systems include the amount of rainfall available, the size

of catchment areas (i.e. roof catchments/hard-standing areas) and the number of people

living within the development. There are examples of these systems being employed in

other countries such as Japan, where the installation of such technology is considered

routine. The Roppongi Hill development in central Tokyo is a mixed use development of

residential, retail, hotel and business units, where a large scale system of greywater and

rainwater reuse is in place. Around 43 per cent of water use across the development is

provided from these sources58.

Within England and Wales there are examples of integrated systems, which capture

rainwater and recycle greywater within a development. The objective of such systems is to

make a development self-sufficient. Two examples from England and Wales are the

ecological Hockerton Housing Development, Nottinghamshire59, UK and the Childwall Estate

Redevelopment in Liverpool60. There are drainage implications for integrated systems.

Normally all overflows discharge to the foul sewer network as the two non-potable sources

may be mixed in the same tank. This means that the water is not of sufficiently good quality

to be discharged into water courses. It may be possible for a combined system to have an

overflow into storm drain, but only if it is guaranteed that the rainwater will not be mixed with

greywater when overflowing. This may involve using a diverter valve.

56

Domenech, L. and D. Sauri. (2010). Socio-technical transitions in water scarcity contexts: Public

acceptance of greywater reuse technologies in the Metropolitan Area of Barcelona. Resources,

Conservation and Recycling Volume 55, Issue 1, November 2010, Pages 53-62.

http://www.sciencedirect.com/ 57

Canadian Water and Wastewater Association. (CWWA). (2002). Research Highlights: Rainwater Harvesting and Grey Water Reuse. Technical series 03-100. http://www.cmhc-schl.gc.ca/publications/en/rh-pr/tech/03-100-e.htm.

58 Greater London Authority (2007) Water matters. The Mayor‟s Draft Water Strategy Draft for consultation with the London Assembly and functional bodies. GLA. London.

59 www.hockertonhousingproject.org.uk and Environment Agency (2010). Harvesting rainwater for domestic uses: an information guide

60 joint winner in the 2004 Sustainable New Homes Awards

http://www.sciencedirect.com/science/journal/09213449

http://www.sciencedirect.com/science/journal/09213449

http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235994%232010%23999449998%232400748%23FLA%23&_cdi=5994&_pubType=J&view=c&_auth=y&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ee3f284b42b5ad35fbe464ff569b19c1

http://www.hockertonhousingproject.org.uk/

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Recommendations – Action plans

8.2 Actions to achieve increased use of non-potable water supply

systems

Local and national programmes to support the expansion of rainwater harvesting /

greywater reuse systems could increase uptake. It is recommended that the

Department for Communities and Local Government review planning policy and

guidance that strongly encourages rainwater and greywater systems in new

development. These policies could be targeted at areas where the water savings and

wider benefits would be of most value61, for instance in London and the South East.

Local Planning Authorities should be encouraged by the Government to incorporate

the new guidance in their Core Strategies to increase uptake of rainwater and/or

greywater systems, in developments that are suitable in their local area. Alternatively,

these requirements could be brought into policy through Local Authority

Supplementary Planning Documents. In 2009 the London Development Agency (LDA)

commissioned a study to better understand if non potable supplies were feasible in

different types of building within London62. It is recommended that other Planning

Authorities follow this example to understand the opportunities, costs, and benefits of

bringing these non potable systems into mainstream planning.

The feasibility of rainwater harvesting and greywater reuse, together with sustainable

drainage systems, should be assessed in the earliest possible stages of development.

The most effective way to ensure that non-potable systems are planned and designed

from the outset is for the construction client to specify this in their original brief. The

likelihood of this happening will increase if Local Planning Authorities include a

requirement for feasible non-potable systems in their planning policies. The planning

process needs to be flexible enough to recognise that non potable systems are not

feasible in every situation.

The Government (for example CLG) should seek opportunities to work directly with the

major development companies to research and produce guidance that will support

developer portfolios including non potable systems as standard, where feasible.

Central and Local Government should work together with developers to share

knowledge on how (and whether) rainwater systems can be integrated within surface

water management plans for new developments, particularly for sites that are subject

to strict surface runoff criteria.

61

Environment Agency (2010). Energy and carbon implications of rainwater harvesting and

greywater recycling. 62

London Development Agency (2009). Managing Water - Reducing Water Demand. Technical

Report (Entec, unpublished).

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Maintenance of non-potable systems is a perceived barrier to uptake. Government

should facilitate discussion between developers and systems manufacturers to better

understand the actual maintenance requirements of different systems so that

appropriate long terms maintenance plans can be developed and agreed where these

systems are being fitted.

The Government should promote the ECA tax relief on rainwater harvesting systems.

Greywater reuse systems do not attract the ECA benefit of rainwater systems;

however, their installation and use can still reduce both the demand for wholesome

water and drainage discharge. At present, their installation as a retrofit together with

their frequent maintenance requirements suggest that any financial saving will be

small, leading to a long payback period. Although greywater systems have the

potential to save up to 30 per cent of water, a number of issues need to be resolved,

including the return to sewer charges, before greywater systems are widely accepted.

It is important to continue to educate and engage customers in water efficient

behaviours and to tackle the perceptions surrounding the feasibility and acceptability of

rainwater harvesting and greywater reuse. Water companies have a key role and

opportunity to issue information to their customers on water resources and the need to

conserve water. Many people still believe that it is not necessary to be water efficient

in England and Wales because there is plenty of rain. People need to become more

familiar and comfortable with these technologies and so public buildings that have

them installed should advertise this more.

The MTP should support and encourage the water companies who are actively

involved in educational activities to promote alternative sources of water, such as

rainwater butts for home use and the cost saving potential of greywater and rainwater

systems.

Various incentives could be considered to increase appropriate uptake, as seen in

other countries. Options include:

Financial incentives:

- Subsidising the installation (rebate);

- Purchase tax incentive (lower VAT);

- Council tax incentive (lower rateable value);

- Lower water charges;

- Higher stamp duty threshold for homes with an alternative water supply; and

- Code for Sustainable Homes.

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Whilst some of these options may not appear feasible in the current economic climate

(2011), they should be considered, and not dismissed as unrealistic.

Public attitudes towards harvested rainwater and greywater are important for their uptake.

Studies have shown that there is generally a positive attitude to the use of recycled water for

toilet flushing63 but that with more “personal” uses e.g. garden watering, the acceptability

decreases. In communal reuse schemes studies have found that users prefer to reuse their

own greywater rather than someone else‟s64. Research suggests that where communal

systems are installed, people prefer larger „city wide‟ schemes where the source of the water

is anonymous rather than local schemes where they may know many of the people

involved65.

8.3 Actions to resolve outstanding data gaps or other issues

The Environment Agency report examining the „Energy and carbon implications of

rainwater harvesting and greywater reuse‟ presents the carbon footprint of water

supplied by „non-potable‟ systems compared to mains water. However, more

information is required on the likely energy costs to the homeowner of running a

greywater or rainwater system. If the energy costs are too high to the customer, this

may exceed the saving on water bills.

Both the rainwater and greywater reuse British Standards have embedded water

quality parameters for water reuse applications to ensure public health is not

compromised. This is the first time that water quality requirements have been included

and should set a precedent that water quality is a mandatory expectation.

63

Hills, S., Birks, R., and McKenzie, B. (2002a). The Millennium Dome “Watercycle” Experiment: to evaluate water efficiency and customer perception at a recycling scheme for 6 million visitors. Wat. Sci. Tech., 46(6–7), 233–240; and Ogoshi, M., Suzuki, Y. and Asano, T. (2001) Water reuse in Japan. Wat. Sci. Tech., 43(10), 17–23.

64 Jeffrey, P, 2002 Public attitudes to in-house water recycling in England and Wales, Journal

of the Chartered Institution of Water and Environmental Management, 16, 214-217. 65

Po, M, Kaercher J D and Nancarrow B E, 2003 Literature Review of Factors Influencing Public Perceptions of Water Reuse. CSIRO Land and Water, Technical Report 54/03. http://www.clw.csiro.au/publications/technical2003/tr54-03.pdf

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Appendix A

Product descriptions

A.1 Rainwater harvesting

There are three basic types of rainwater harvesting systems66:

Water collected in storage tank(s) (i.e. at ground level or underground) and pumped

directly to the points of use;

Water collected in storage tank(s) (i.e. in roof spaces) and fed by gravity to the points

of use; and

Water collected in storage tank(s) (i.e. at ground level/underground), pumped to an

elevated cistern and fed by gravity to the points of use.

Within these basic types, there are variations such as:

Internal or external locations for tanks;

Single or multiple linked tanks;

Freestanding or fully buried or partially buried tanks;

Communal tanks supplying multiple properties; and

Packaged systems or components.

Rainwater collection area/rainfall/storage

Rainwater may be harvested from roofs and hard-standing, such as driveways and can

either be stored underground or in roof spaces. Storage in the roof space enables flow to

fixtures such as WCs to be via gravity, however this option is generally ruled out because of

limited space (and therefore storage) and the implications that additional loading from a

large water tank has on construction design, methods, materials and cost. These factors

mean that conventional household rainwater systems generally have underground storage

tanks located adjacent to the property, e.g. underneath the rear garden.

The roof or catchment area for collecting rainwater, the average annual rainfall and

distribution through the year and materials the roof or catchment area are constructed from

will determine the available yield of rainfall. Local rainfall data may be available from the

Environment Agency or the Met Office. For domestic application, rainwater storage tanks

are commonly sized at 5 per cent (0.05) (This represents 5 per cent of the year (18 days) of

the rainwater supply or of annual demand, using the smallest of the figures.

66

BS 8515: 2009. Rainwater harvesting systems – Code of practice.

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The size of tank needs to be large enough to maximize the use of rainwater during dry

periods, but to allow overflow at least twice per year to flush out debris. More detailed

calculation methods are given in CIRIA guidance67.

When calculating yield, the total „catchment area‟ should take account of both: roof area in

m2 and; if used, the runoff water from a hard-standing area into a sustainable drainage

system. A drainage coefficient (runoff factor) is used to adjust the efficiency of collection

and, therefore, the required size of tank. Filter efficiency will also have an effect on the

harvested quantity.

Tanks should be located to avoid extremes of temperature, as higher temperatures could

encourage bacterial growth in the stored water, and freezing conditions can damage the

tank. Tanks tend to be stored underground, and sufficient space needs to be available in the

development layout. A typical tank volume for a single household is 1.0 to 3.0 m3.

Rainwater pumping mechanisms

Rainwater is usually pumped from the underground storage tank to a header tank located at

high level. A similar arrangement is commonly used for greywater. In the event that the

alternative water supply cannot meet demand though lack of rain or pump failure, mains

water must be available to top up the tank via a required type AA air gap. Some appliances

can be adapted for a connection to both wholesome and a non-wholesome water supply

(e.g. a WC cistern may be adapted for dual feed, provided that a type AA air gap is provided

to prevent mains water contamination). The rainwater supply pump can either be a

submerged unit in the main storage tank, or a suction pump outside it.

Suction pumps are usually located within the control unit and must be positioned relatively

close to the tank, in frost-free conditions. Automatic sensors are usually used to activate the

pumps to replenish the header tank or directly refill a WC cistern.

Sensors to protect pumps from dry running should also be considered. Filters are the first

line of treatment, initially preventing solid debris from entering the holding tank. Finer

downstream filters may be required depending on the uses to which the alternative water

supply is to be put.

All pipe-work carrying non-wholesome water must be clearly marked. All installations must

comply with the Water Regulations.

Individual or shared systems

Rainwater harvesting can be installed for individual households, or on a larger scale where

water is collected from a number of properties (for example in a street), treated centrally then

pumped to individual households for reuse.

67

CIRIA (2001) Rainwater and Greywater Use in Buildings: Best Practice Guidance. Report C539. CIRIA, London

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The benefits are savings in potable water use and discharge rates to sewers, and reduced

runoff rates and consequent risk of surface water flooding from new developments.

Planning policy now requires that sustainable drainage systems are used in new

developments where possible to reduce flood risk, and rainwater harvesting can contribute

to sustainable drainage design68.

Advantages of a centralised system over single household units may include that:

Water is collected from areas of hard-standing within the development, for example

walkways and paved areas, which increases the volumes collected for re use; however

water collected from these areas may need more treatment, to remove pollutants from

roads, compared to water collected only from roofs;

Collecting rainwater from paved communal areas will reduce rainfall runoff further;

The system is likely to be maintained by qualified personnel (e.g. a service contractor)

rather than individual householders;

There will be cost savings in installing large communal systems (due to economies of

scale) compared with installing individual households covered by the communal

system.

However, there may be a user perception that they don‟t want to use communally collected

water.

Rainwater harvesting systems need to be maintained and if single household units are

installed the householders will be responsible for this. BS 8515 recommends checks once

per year, but filters may need cleaning more often and gutters need to be kept free from

debris. The mains back-up should be checked once per year for correct functioning. Hence

these are not (and never will be) fit-and-forget systems, and house owners/occupiers will

need a level of commitment to keep them operating.

Where communal systems are installed a contractor will need to be employed to maintain

the system, and the costs of responsibility and payment for maintenance should be

considered early in design phase of any system. Options include charging residents of a

development a maintenance fee for the upkeep of the system. This is likely to be relatively

straightforward in social housing developments, where maintenance costs could be collected

and administered by the organisation responsible for the housing (e.g. a housing

association). In private developments a maintenance contract may need to be agreed on

purchase of the property, with maintenance being administered by a private company.

68

Communities and Local Government (2006) Planning Policy Statement 25: Development and Flood

Risk. Communities and Local Government. Wetherby.

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A.2 Greywater reuse

Greywater reuse systems vary significantly in their complexity and size from small systems

with very simple treatment to large systems with complex treatment processes. However,

most have common features such as:

A tank for storing the treated water;

A pump;

Water treatment; and

A distribution system for transporting the treated water to where it is needed.

All systems that store greywater have to incorporate some level of treatment, as untreated

greywater deteriorates rapidly in storage. The tank should also incorporate a mains water

connection for when supply does not meet demand and this must include backflow

protection, in order to comply with the Water Supply (Water Fittings) Regulations 1999 and

prevent contamination of the mains supply.

Types of greywater system

A recent Environment Agency report69 recognises five broad types of greywater systems:

Direct reuse systems;

Short retention systems;

Basic physical and chemical treatment systems;

Biological treatment systems; and

Biomechanical systems.

Direct re-use systems include storage of very short duration. This could include using

water from kitchen sinks or baths directly in the garden. This does not require advanced

technology (a bucket or a siphon hose can be used), and items such as the Watergreen70

have been developed to facilitate this. This simple approach of using a siphon hose is a

short term measure (marketed as a drought measures) and is not a fit and forget technology

suitable for inclusion in new developments.

Short retention greywater systems, such as Ecoplay71 use settlement or skimming

technology to remove materials from greywater, but do not provide any further treatment.

When untreated greywater is retained, even for short periods, bacteria can build up causing

69

Environment Agency (2008). Greywater: an information guide. Environment Agency. Bristol 70

www.droughtbuster.co.uk 71

http://www.ecoplay-systems.com . Other systems are available.

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odour and water quality issues. It is, therefore, undesirable to have a large storage tank.

Short retention systems release unused greywater from storage to waste to avoid these

problems. Mains water is then used in its place. The collection/holding tank for grey/

recycled water should be positioned in a relatively cool but frost-free environment to

minimise bacterial growth.

Basic physical and chemical systems provide simple filtration and chemical disinfection

treatment to greywater. This enables more greywater to be stored for longer periods of time

and thus offer a greater potential for minimising demand in new developments. The systems

require more storage space for tanks than short retention systems due to the volume of

greywater that can be stored. Provision for the storage tank will need to be incorporated into

the design of a building for individual property systems. Storage tanks are normally located

outside the building either buried within the garden or as an above ground tank, similar in

appearance to a water butt. Greywater collects in the storage tanks and is pumped to a

header tank located within the roof space of a property. The water is then supplied via

internal plumbing, usually for the purposes of toilet flushing.

Biological treatment systems, such as the Green Roof Water Recycling System, GROW72,

use naturally occurring bacteria to treat greywater. By employing such processes a

biological greywater system is essentially performing the same functions as an on-site

sewage treatment works. The most common form of biological treatment is passing

greywater through reed-beds where bacteria in the plant root systems break down organic

waste using oxygen supplied by plants. This is a well established method for treating

wastewater, and reed-beds can provide amenity and ecology value, although they do require

relatively large areas of land. For this reason they may not be suitable for some new

developments in the highly urbanised areas.

Bio-mechanical systems are the most advanced greywater treatment systems and perform

similar functions to an on-site sewage treatment works. An example system is the Pontos

Aquacycle73, which filters greywater from baths and showers before a two stage treatment

process of where micro-organisms break down organic material. The partially treated water

is then settled and disinfected with ultraviolet light. The manufactures claim that the treated

water is suitable for use in toilet flushing, washing machines, cleaning and garden watering.

The Aquacycle technology is available for application at different scales, with single

domestic units such as the Aquacycle 900 to the AquaCycle 13,500 with a 13,500 litres/day

capacity, suitable for development level installation or use in larger commercial properties.

It is the basic physical and chemical treatment systems that have been most widely applied

in trials in the UK at the individual household level. Findings have been published from a

number of trial studies such as a national trial by the Environment Agency74, and a study by

72

http://www.wwuk.co.uk/grow.htm 73

www.ribaproductselector .com/docs/1/11501/external/COL311501.pdf?ac= 74

Environment Agency (2000) A study of domestic greywater recycling. Environment Agency. Worthing.

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Cranfield University and Thames Water in Aylesbury75. Most studies report technical issues

relating to the reliability of the systems and the quality of greywater captured.

There are also issues relating to public perception of greywater reuse and the performance

of the systems impacting on the residents in households where such systems have been

installed that many would deem unacceptable. Few of the individual greywater systems that

have been trialled within the UK have collected water from the kitchen due to the presence

of fats within the wastewater stream. These can collect and block the filter systems76.

Greywater systems can be implemented at the individual property level or as communal

systems at the development level. At the individual property level, there are concerns over

the reliability and performance of systems. The issues are likely to be minimised if

greywater systems are implemented at the communal level, since established treatment

technologies akin to those that are tried and tested in sewage treatment processes could be

implemented. However, there could still be issues of resident acceptability over the concept

of using other residents treated wastewater that may prove a barrier to implementation in

new developments.

A.3 Maintenance

An alternative water supply is not a „fit and forget‟ technology, maintenance schedules must

be adhered to in order to keep a system running correctly and avoid bacterial growth and

contamination. Maintenance should, therefore, include:

General cleaning and maintenance of rainwater collection areas;

Removal of debris that could block a system;

Annual visual inspection of the system components;

Cleaning/replacement of filters in accordance with the manufacturer‟s

recommendations;

Regular checks on greywater disinfection in accordance with the manufacturer‟s

recommendations; and

Checks that the mains water top-up is functioning

75

Jeffrey, P. (2005) Assessment of water savings from single house domestic greywater recycling systems, IWA 2nd International Conference on Efficient Use and Management of Water in Urban Areas, held in Tenerife, Canary Islands, 2004. ISBN: 1843394669. IWA Publishing.

76 Environment Agency (2000) A study of domestic greywater recycling. Environment Agency.

Worthing.

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Appendix B

Environmental benefits

B.1 Reduced water consumption

In the short term, water conservation devices and water efficient products offer greater

financial and water saving benefits. However, in the longer term, the financial and

environmental benefits for the water-stressed areas of England and Wales may well shift the

balance in favour of alternative water supplies.

B.2 Reduced energy consumption

There are three primary areas of energy use with regard to water:

Energy embodied energy in the water supplied;

Energy used to heat domestic hot water and for central heating; and

Energy used in appliances (e.g. dishwashers, washing machines, shower pumps).

Rainwater and greywater systems avoid using the embodied carbon in potable water, but

they have their own carbon footprints which vary depending on system type, installation

arrangements, and the level of demand. Pumping requirements are the main factor.

Greywater also has on-site treatment issues such as the release of chemicals/disinfectants

into the foul drainage system.

B.3 Support sustainable drainage

Rainwater systems reduce the volume of rainwater that drains directly from buildings. The

water will be released at a slower steady rate as dictated by flushing frequency, and passes

into the foul sewerage system, rather than surface water drains (for new developments, at

least).

In addition to the strain on water resources, there are also concerns about rainwater

drainage from urban areas. Planning authorities are required to consider the effects of

surface water drainage and the potential impact on flood risk, (in England, Planning Policy

Statement (PPS25)). This means that traditional combined sewerage approaches are no

longer acceptable in new developments. Rainwater harvesting can contribute to an overall

approach to sustainable urban drainage systems (SUDS).

For a larger scale system, greywater may be treated in the same way as sewerage using

traditional biological methods combined with modern filtration methods. Such a system may

be combined with a sustainable drainage system as a concept at a building‟s design stage

rather than post construction retrofit. The economy in both the reduction of water and

sewerage charges may tip the financial balance in favour of such a system.

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Reclaimed water systems can play a part in water conservation by reducing the amount of

mains supplied water used in the home and non-domestic buildings. However, it is vital to

ensure that the design, installation and maintenance of such systems do not compromise

public health by contamination of the wholesome mains water supply through inadvertent

cross-connection or backflow. Installations must, therefore, comply with the Water Supply

(Water Fittings) Regulations 1999 in England and Wales and Approved Document H of the

Building Regulations.

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Related MTP information

MTP (2007). Rainwater and Greywater: review of water quality standards and

recommendations for the UK

MTP (2007). Rainwater and Greywater: technical and economic feasibility

MTP (2007). Rainwater and Greywater: a guide for specifiers

Changes from earlier version

This briefing note replaces the following previous briefing notes:

BNWAT19: Alternative sources of water – greywater and rainwater reuse: Innovation

briefing note

Consultation and further information

Stakeholders are encouraged to review this document and provide suggestions that may

improve the quality of information provided. Email [email protected] quoting the

document reference, or call the MTP enquiry line on +44 (0) 845 600 8951.

For further information on related issues visit http://efficient-products.defra.gov.uk