cpcpwt4022a commission and maintain backflow prevention...

Commission and maintain backflow prevention devices

© Commonwealth of Australia 2015 1

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ACKNOWLEDGEMENTS

National Plumbing Services Training Advisory Group

Plumbing Industry Commission Victoria

© Commonwealth of Australia 2015

Construction and Property Services Industry Skills Council

PO Box 151 Belconnen ACT 2616 Tel: 02 6253 0002 www.cpsisc.com.au This work is copyright, but permission is given to trainers and teachers to make copies and contextualise the resources for use within their own training organisation or in a workplace where training is being conducted. This permission does not extend to making copies for use outside the immediate training environment for which they are made, or the making of copies for hire or resale to third parties.

The work was first published in 2006 with the assistance of funding provided by the Commonwealth Government, through the then Department of Education Science and Training (DEST). The 2015 publication has been updated to reflect changes to the national units of competency.

The views expressed in this work do not necessarily represent the views of the Commonwealth of Australia or CPSISC. In addition, the Commonwealth of Australia and CPSISC do not give warranty or accept any legal liability in relation to the content of this work.

The website addresses and other contact information provided in this publication were compiled in good faith and were correct at the time of printing.

The updating of these resources was completed by:

National Plumbing and Services Training Advisory Group, with funding and support provided by the Construction and Property Services Industry Skills Council (CPSISC):

This guide was developed in consultation with representatives of the Plumbing Industry by NPSTAG and CPSISC to support the implementation of the CPC08 Construction, Plumbing and Services Training Package.


2 © Commonwealth of Australia 2015

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Acknowledgements

Project reference committee: National Plumbing Services Training Advisory Group

Writer: Paul Carey, Stephen Parker

Technical editor: Rodney Jackson

Instructional designer: Judie Litchfield

Graphic artist: Laura Bito

Word processor: Melissa Rogers



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Contents

Before you begin........................................................................................................ 5

Introduction ............................................................................................................... 9

1. Hydraulics and hydrostatics as they relate to BPD .............................. 10

1.1 Hydraulics – The study of fluids in motion ............................................. 10

1.2 Hydrostatics – The study of fluids at rest ................................................ 10

2. Introduction to backflow prevention devices ........................................ 12

2.1 What is a backflow prevention device? .................................................... 12

2.2 Components and materials ........................................................................ 15

2.3 Statutory requirements for BPDs .............................................................. 16

3. A range of backflow prevention devices ............................................... 18

3.1 Check valves ................................................................................................. 18

3.2 Pressure-type vacuum breakers (PVB) ..................................................... 19

3.3 Reduced pressure zone devices (RPZ) ..................................................... 20

3.4 Registered break tanks (RBT) ..................................................................... 22

3.5 Registered air gaps (RAG) .......................................................................... 22

3.6 Line strainers ................................................................................................ 23

3.7 Isolation valves ............................................................................................ 24

4. Preparing for the job ................................................................................ 25

4.1 Know what must be done .......................................................................... 25

4.2 Plan the specific tasks ................................................................................. 26

4.3 Have equipment ready ............................................................................... 26

4.4 Plan for safety ............................................................................................... 28

4.5 Prepare the work area ................................................................................. 28

4.6 Required certification .................................................................................. 29

4.7 Quality assurance requirements ................................................................ 29

4.8. Identifying testing and commissioning requirements ........................... 32



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5. The testing and commissioning procedure ............................................ 35

5.1 A basic installation ...................................................................................... 35

5.2 Basic test procedures ................................................................................... 36

5.3 The reduced pressure zone device (RPZ) ................................................ 38

5.4 The pressure vacuum breaker (PVB) ........................................................ 42

5.5 Test completion ............................................................................................ 43

6. Maintenance .............................................................................................. 48

6.1 Meeting requirements ................................................................................. 48

6.2 Safety ............................................................................................................. 49

6.3 Following appropriate workplace procedures ........................................ 49

6.4 Quality assurance: whose responsibility? ................................................ 50

6.5 Required certification .................................................................................. 50

6.6 The procedure .............................................................................................. 50

6.7 A checklist of common faults and remedies ............................................ 52

7. Finalisation procedures ............................................................................ 57

7.1 Restoring the work area .............................................................................. 57

7.2 Waste disposal ............................................................................................. 58

7.3 Restoring equipment and tools to good working order ........................ 58

7.4 Documentation ............................................................................................ 58

Final assessment activity ................................................................................... 60



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Before you begin

Welcome

Welcome to the learning resource for the unit CPCPWT4022A Commission and maintain backflow prevention devices. This resource will help you develop the knowledge and skills you need to demonstrate competence in this unit.

A learning resource such as this is not intended to be the only source of information you use to develop skills and knowledge in the unit it relates to. Your trainer, instructor or supervisor will provide you with additional information and information sources throughout your training.

Flexible delivery

Your trainer, instructor or supervisor for the unit may adapt and deliver this learning resource as required to suit people from a range of backgrounds and in diverse learning environments (such as rural and isolated settings). This will assist in meeting equity principles and conforming to legislative policies.

How to use this resource

This resource addresses the underpinning knowledge and skill development required to help you commission and maintain backflow prevention devices. It contains:

• information on commissioning and maintaining backflow prevention devices

• activities designed to encourage you to check and confirm your learning along the way and to help you complete the final assessment

• a summary of the final task or tasks you must complete to be assessed as competent in this unit. Your assessor will give you the additional specific detail required for your final assessment activity in line with state and territory regulations and industry requirements.

The resource has been developed for use in a variety of ways. Your trainer, instructor or supervisor will advise on how best to use it during your training, which may include:

• teacher-centred, class-based study

• home-based, self-directed study

• activities in the workplace.



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To complete the unit CPCPWT4022A Commission and maintain backflow prevention devices you may be required to:

• read the information in this resource

• complete the resource activities as directed and submit your answers for review or discussion with your trainer, instructor or supervisor

• work with your trainer, instructor or supervisor to practise commissioning and maintaining backflow prevention devices

• read the final assessment summary together with any additional assessment information your assessor provides

• complete the final assessment.

Your assessment in this unit

It is important to note that the role of the assessor in assessing units of competence is quite separate from the role of trainer, instructor or supervisor. Your assessor for this unit may or may not be the same person as the trainer, instructor or supervisor who worked with you during your training. However, your assessment must always meet the requirements of the unit. You will find references to trainers, instructors or supervisors and assessors throughout this resource depending on the context.

Assessment in this unit will require you to demonstrate the skills and knowledge needed to commission and maintain backflow prevention devices. Table 1 on page 3 suggests the variety of assessment methods that may be used to assess your competence in this unit. In many instances, your assessment may involve a combination of methods to ensure the validity, reliability, flexibility and fairness of the process. If you have any questions about your assessment please discuss them with your assessor who will decide with you the specific details of what you will do. An assessor may develop specific assessment strategies to meet the particular requirements of learners from diverse backgrounds.

This unit may be assessed in conjunction with assessment for other units of competence. In such a case assessment might be based on a task or tasks related to a project that more closely resembles workplace activities. An appropriate unit for such project-based assessment might be one that naturally forms part of your workplace responsibilities and roles. Your assessor will decide if you are to be assessed in this way and will advise you.



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Assessment methods

Key Assessment

method Description

QS Questioning oral/written

Assessor will ask a range of questions from a moderated bank of questions that support the underpinning skills and knowledge required to achieve competency in this unit. Questions may be answered in written or oral form.

WN Written notes Learner will complete written notes, activities or student resource materials to support the achievement of underpinning knowledge required to achieve competency in this unit.

TB Test bank Learner will complete computer test bank assessment which supports the underpinning skills and knowledge required to achieve competency in this unit.

PO Practical observation

Assessor will observe the learner completing practical task(s) that meet the assessment criteria to the required specification in the workplace.

DM Demonstration Assessor will observe the learner completing practical task(s) that meet the assessment criteria to the required specification in a simulated work environment.

CS Case study/project Learner will complete workplace-based projects or case study reports to support the underpinning skills and knowledge required to achieve competency in this unit.

LB Logbook Learner will provide evidence of practical work and/or assessment tasks completed at the workplace via personal logbook.

3P Third party report Assessor will seek report from learner’s workplace employer, supervisor or other approved party on the performance of a learner in the workplace against assessment task criteria and requirements of the unit.

WD Workplace documents

Learner will provide copies of workplace documents to support the underpinning skills and knowledge required to achieve competency in this unit.

Table 1 – Assessment methods



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Prerequisites units

There are no prerequisite units for this unit. However this unit has a relationship with the unit CPCPCM4011A Carry out work based risk control processes.

Additional resources

The following resources have been suggested that may help you undertake training and assessment in this unit. Your trainer/instructor/supervisor may also recommend specific books, videos and DVD’s.

Note

Standards, websites and codes of practice change, so it is important to keep up to date. Make sure you always have the most recent edition of the Standards applicable to your current job. You should also obtain relevant manufacturer information.

Texts

• Building Code of Australia

• Plumbing Code of Australia

• AS/NZS 3500 – Plumbing and drainage

• AS/NZS 2845.1 - Water Supply – Backflow prevention devices – materials, design and performance requirements

Websites

Video or audio resources



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Introduction

The delivery of water services is based on the sound application of engineering and plumbing skills and this is very much so with work on backflow prevention devices.

The testing, commissioning and maintenance of backflow prevention devices in water services is based on clever innovations which are not apparent to the casual observer. Even plumbers who work with these devices don’t always realise that the ingenuity in them can be traced back to ancient cities such as those of the Roman Empire, where engineering genius and the skills of the early plumbers were applied to erect great baths and recreation centres that used water supplied by aqueducts from sources many miles away.

This unit covers the testing, commissioning and maintenance of backflow prevention devices (BPD) in water services. The content includes preparing for work, identifying testing and commissioning requirements, actually testing and commissioning the devices, maintaining them and finalising work processes. The unit has been designed to help you develop the skills and knowledge to identify levels of risk/hazard, select the appropriate backflow prevention device for the job, as set out in AS/NZS 3500, and then do the required work. While a registered or licensed person can install any of these devices, commissioning, testing and annual retesting must be done and documented by someone licensed to test backflow prevention devices. This is a legal requirement.

As you work through the unit, you will complete activities that will help you meet many of the requirements for demonstrating competency. For assessment, you will test and commission at least six devices, incorporating double check valves, pressure-type vacuum breakers and reduced pressure zone devices. Your work will cover situations with low, medium and high risk of contamination to drinking water and you will be required to assess the ongoing maintenance requirements for each device. Throughout, you will need to show you can correctly identify what is needed, work out what you need to do the job and then do it. Your work must be to specification and must comply with relevant regulations, standards and organisational requirements.



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1. Hydraulics and hydrostatics as

they relate to BPD

1.1 Hydraulics – The study of fluids in

motion

Water flow through a pipe is affected by friction restricting the volume of water delivered at the outlet. For example, in a long length of cement-lined and steel water mains, the laws of hydraulics apply when rust and scale build-up increases friction as water flows through the pipe. By contrast, smooth-bore pipes of materials such as copper, polyethylene and PVC-U minimise friction between the pipe wall and the water. Short-radius bends, elbows and tees used to change pipe direction similarly cause friction. Pressure loss caused by this friction can be minimised in a variety of ways. Long-radius bends are used where possible. Pipe ends are de-burred. Care is taken to fully engage pipes into sockets and to avoid poor joints. Lever action ball valves or gate valves are preferred to stop taps as they offer less resistance to water flow.

1.2 Hydrostatics – The study of fluids at

rest

The pressure exerted by water at the base of a tank is determined by the depth of the water, or the height of a tank above a water outlet. For example, a header tank ten metres above an outlet has a pressure of 981 kPa at that outlet, or 9.81 kPa for every metre head (the measure used to measure pressure when water is static).

Activity 1

1. In the space below, work out the pressure at the base of a column of water 23 metres high.



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2. A water supply tank is located in the ceiling space of a building. The tank is 4.0 metres above the lowest water outlet and the highest outlet in the building is 1.2 metres above floor level. In the space below, calculate the pressure at both outlets.



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2. Introduction to backflow

prevention devices

To work on backflow prevention devices, you need a good understanding of the range of devices and how they are used.

2.1 What is a backflow prevention device?

A backflow prevention device prevents the reverse flow of water from a potentially polluted source into the drinkable water supply.

The device required in a particular situation depends on how great the risk (or ‘hazard’) is assessed to be. Cross-connections between elements in a system are rated high, medium or low risk.

High hazard Any condition, device or practice that might affect a drinking water supply system in a way that could cause death.

Medium hazard Any condition, device or practice that might affect a drinking water supply system in a way that would endanger health.

Low hazard Any condition, device or practice that might affect a drinking water supply system in a way that would create a nuisance but not endanger health or cause injury.



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Activity 2

Study Appendix F in the Australian Standard AS/NZS 3500.1 - Water Services, and then answer the following questions.

1. What hazard rating does a pressure-type vacuum breaker have?

2. List two situations where a pressure-type vacuum can be installed.

3. What hazard rating does a reduced pressure zone device have?



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4. List two situations where a reduced pressure zone device can be installed.

5. What hazard rating does a double check valve have?

6. List two situations where a double check valve can be installed.

7. What hazard rating does a registered break tank have?



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8. List two situations where a registered break tank can be installed.

9. What hazard rating does a registered air gap have?

10. List two situations where a registered air gap can be used.

2.2 Components and materials

Any part of a backflow prevention device that will contact water must comply with ‘dezincification-resistant’ requirements of AS 2345. ‘Dezincification’ is the corrosion of copper/zinc alloys involving loss of zinc and a residue of spongy or porous copper. A dezincification-resistant copper/zinc alloy has a chemical composition and physical characteristics that meet the dezincification requirements of the Australian Standards.

If the device will contact drinkable water, its components must comply with AS 3855 (Int). Components not in contact with water may be made from materials other than those specified in that section.



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Metals used include:

• silver brazing alloy complying with AS/NZS1167.1

• copper phosphorus brazing alloy with a minimum of 1.8% silver and complying with AS/NZS1167.1

• tin silver solder complying with AS 1834.1 for Grade 96.5 Sn 3.5 Ag

• tin copper solder complying with AS 1834.1 for Grade 99.3 Sn 0.7 Cu.

Where it is impracticable to use similar metals (including metal-filled plastics) for the entire device, steps must be taken to prevent the formation of electrolytic galvanic couples. For example, fittings may have to have insulating washers to prevent electrolytic action.

External plastic components must be self-extinguishing and resistant to ultraviolet degradation over the recommended mechanical life of the valve.

2.3 Statutory requirements for BPDs

A BPD must be installed in a way that minimises the risk of damage to the device and injury to whoever will test and/or maintain it.

It may be located:

• at a specific hazard (‘individual protection’)

• on cold water piping to more than one hazard (‘zone protection’)

• at the property boundary after the meter (‘containment protection’).

AS/NZS 3500 and AS/NZS 2845 set out the main requirements for location and installation of BPDs. In particular, you should study AS/NZS 3500 Clause 4.6.2. The following is a guide:

• They must not be located in a corrosive or polluted atmosphere, where contaminated air can enter the piping system through the air gap or open vent port and make the device malfunction.

• They must not be buried in the ground.

• Vented testable BPDs must not be located in pits or in cabinets without drainage.



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• Containment devices must be located as close to the water meter outlet or property boundary as practicable. There must be no branch connection between the meter and the device.

• Insulation or any other protection of the device must not prevent its proper operation, testing or maintenance.

• If water hammer occurs, it should be stopped. This is done by installing a surge protector or water hammer arrestor.

• All inline devices must have connections that allow removal and replacement of the device.

AS/NZS 3500 Clause 4.6.2.2 sets out the requirements to ensure devices are easily accessible for maintenance or testing without ladders or scaffolding.

Note

Your trainer/instructor/supervisor may refer you to other resources for additional information on requirements for BPDs.

Who has responsibility?

Manufacturers must make sure their valves comply with AS/NZS 2845.1.

Suppliers should understand what they are selling and only sell BPDs approved by the relevant authorities for the intended application.

System designers should have up-to-date information on approved BPDs, installation requirements and applicable codes. They should check with local or regional authorities to find out whether the system must be approved before connection to the reticulation system.

Plumbers must have endorsed registration in Water Supply Plumbing. They must understand the devices they work with and installation requirements.

Your trainer/instructor/supervisor may refer you to other resources for additional information on requirements for BPDs.



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3. A range of backflow prevention

devices

3.1 Check valves

A double check valve provides protection to the drinkable water supply from contamination in medium-hazard applications such as industrial, commercial and medical equipment. It also monitors unauthorised usage from fire hydrants and sprinkler systems.

The valve prevents backflow caused by backpressure, using two independently operating force-loaded non-return valves. The device also has specific test points for in-service testing.

A double detector check valve may be used in conjunction with a double check valve to ascertain water usage as required by local water authorities.

How check valves work

During normal flow conditions, the two check valves are held open, supplying water downstream. Each check valve is designed to maintain a minimum of 7 kPa across the valve during normal operation. Should the downstream pressure increase to within 7 kPa of supply pressure, both check valves will close as double protection against backflow.

Figure 1 – Double check valve



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3.2 Pressure-type vacuum breakers (PVB)

Pressure-type vacuum breakers help protect the potable water supply from contamination in medium-hazard applications, such as in steam calorifiers, irrigation systems and chlorinators.

The device prevents backflow caused by back-siphonage. It incorporates a force-loaded ventilation valve and operates automatically to admit air into the valve’s downstream chamber whenever pressure in the chamber drops.

How does a PVB work?

Pressure applied to the inlet valve spring opens the inlet valve. This in turn closes off the ventilation valve by forcing it against its seat. Water then flows to the outlet. When the water is turned off or the water pressure falls below 7 kPa, the return spring forces the inlet valve to the closed position. The ventilation valve opens, allowing air to enter the system and break the vacuum. Water then drains from the system via the outlet(s).

Figure 2 – Pressure type vacuum breaker



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3.3 Reduced pressure zone devices (RPZ)

A reduced pressure zone device provides maximum protection to the potable water supply from contamination in high-hazard applications such as cooling towers, abattoirs and sewage treatment plants.

It prevents backflow caused by back-siphonage or back pressure in a water reticulation system.

The device has two independently operating force-loaded non-return valves. It automatically drains to waste whenever the pressure between the upstream and downstream non-return valves drops to 14 kPa or more below the pressure at the inlet to the upstream non-return valve.

A double detector check valve may be used in conjunction with a reduced pressure zone device to ascertain water usage as required by local water authorities



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How does an RPZ work?

During normal flow conditions, the supply pressure on the relief valve diaphragm, acting on the internal bypass passage holds the relief valve shut. The two main check valves are held open, supplying water downstream. In the area between the check valves (the ‘zone’), the pressure is maintained at approximately 49 kPa lower than the inlet supply pressure. Should back-siphonage or back pressure occurs, the second check valve seals, stopping the backflow of water. In the unlikely event that the second check becomes fouled, the pressure in the zone increases, causing the differential relief valve to open to atmosphere. This ensures that the entire backflow discharges to drain and no potentially contaminated water enters the upstream potable water supply.

Figure 3 – Reduced pressure zone device



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3.4 Registered break tanks (RBT)

A registered break tank helps protect the potable water supply from contamination in high-hazard applications, such as in bidets, plant with an auxiliary non-drinking water supply, and in electroplating, degreasing, de-scaling, stripping and dipping tanks, vats and vessels.

A registered break tank is a tank system designed specifically for backflow prevention. It is registered by or on behalf of a regulatory authority to help ensure the inspection and maintenance that keep the system working as it should.

How does an RBT work?

Water in a supply tank has unobstructed vertical distance between the lowest opening of the water service or fixed outlet and the highest possible water level of the tank. This air gap prevents the possibility of backflow and back-siphonage. The gap must be determined in accordance with AS/NZS 3500 Table 4.3.

3.5 Registered air gaps (RAG)

A registered air gap provides protection to the potable water supply from contamination in high-hazard applications such as in food preparation or food storage tanks, cooling towers and dockside facilities.

It is a device or system installed for backflow prevention. It is registered by or on behalf of a regulatory authority to help ensure the inspection and maintenance that keep the device working as it should.

How does a RAG work?

Water in a supply tank has unobstructed vertical distance between the lowest opening of the water service or fixed outlet and the highest possible water level of the tank. This air gap prevents the possibility of backflow and back-siphonage. The gap be determined by AS/NZS 3500 Table 4.3.



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Figure 4 – Break tank and air gap

3.6 Line strainers

A line strainer has a spring-loaded rubber valve which is forced against a brass seat to prevent rust, scale, etc from the reticulation system entering the BPD and fouling or damaging the seats. Obviously, such damage would make the device ineffective in preventing backflow.

Flushing out water supply systems before installation of the BPD also helps minimise the risk of damage to the device.

Figure 5 – Line strainer assembly



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3.7 Isolation valves

AS/NZS 3500 Clause 4.6.1 requires a resilient seated isolation valve immediately upstream of the line strainer when a testable device is installed. If there is no integral line strainer, the device must be immediately upstream of the BPD.

Lever action ball valves are the preferred type as they are soft-seated and offer little resistance to flow. These valves make commissioning and testing, isolation and maintenance procedures possible. The isolation valve needs to be in the fully open position when the water supply is in use (handle facing in the direction of water flow). Alternately, when maintenance on the BPD is needed, the valve must be in the fully closed position (handle at right angles to the direction of water flow). The valve should always be left in the fully open position.



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4. Preparing for the job

Your approach to testing, commissioning and maintenance of BPDs should be much the same as for all plumbing installation work. That is, you should see it as a systematic process with a number of key elements. Any other way of approaching the task will almost certainly result in problems that waste time and may be difficult to fix.

Here are the main steps in the process:

• preparing for the job

• identifying requirements for testing and commissioning

• testing and commissioning the device

• maintaining the device

• restoring the work area.

Each step will be explained in detail in the following sections.

4.1 Know what must be done

Before you begin any work with a BPD, you should familiarise yourself with all relevant standards, drawings and specifications.

As outlined in earlier sections, you should study AS/NZS 3500 and AS/NZS 2845 to learn the requirements for location and installation of BPDs. AS/NZS 2845 Appendices D to AP sets out the test requirements for all testable Backflow Prevention Devices.

Local water authority regulations and requirements must also be considered and you might need to consult a hydraulic engineer’s report to find out what type of system is required (individual, zone or containment). The report might also recommend the specific type(s) of valve(s) to be installed and where.

Note

Always check manufacturer’s specifications. In specific cases, these might override industry regulations and standards.



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4.2 Plan the specific tasks

Work out exactly what must be done and in what order. Consider who will do what and who will be affected by the work.

Hints for effective planning

• Communicate your thoughts as clearly as you can. Use simple English so everyone knows what needs to happen, how it will happen and who is responsible for what.

• Pay attention to how you work with others. Adopt a cooperative, team approach.

• Establish safe and effective work processes that anticipate likely problems and blockages, and systematically work around them to avoid or minimise reworking and wastage.

• Use systematic, simple mathematical ideas and techniques to collate applicable data.

4.3 Have equipment ready

Your work with BPDs will require you to carefully measure, calculate, check for accuracy and record results efficiently. You will also need to carefully calculate materials required. This will involve the use of calculators, levelling systems and a range of other tools and equipment, using the workplace technology which is available to you.

To test a BPD, you will need a test kit similar to the one shown in the diagram that follows. The kit has a differential pressure gauge which you attach to the test taps on the BPD via a series of valves and hoses. You then open and close the valves in a set order, depending on the type of device you are testing.

The differential pressure gauge must be properly maintained. A certified technician must recalibrate it annually (or more often depending on local water authority requirements).



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Figure 6 – Typical test kit



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4.4 Plan for safety

Commissioning and testing a BPD usually means working in an unfamiliar environment. That means you must take care of your own safety and the safety of others. You must know and comply with all relevant OH&S requirements and any Safe Work Method Statement (SWMS).

Before starting the job, clear the work area of any obstructions. If barricades, signage and alternate walkways are needed, make sure they are in place. Use a neon tester to check for stray electrical current in the water supply system. Reduce the risk of electrocution by putting bonding straps on both sides of any disconnection point, and by having rubber matting or timber platforms to kneel on.

Don’t let water discharge from a test point onto any nearby electrical equipment.

If a BPD is installed in a pit, use a gas detection device to be sure the pit holds no poisonous or explosive gases. You must use a harness in conjunction with a tripod and have help readily available in case a dangerous situation arises.

If a BPD is installed in an elevated position, the use of scaffolding reduces risk. If the BPD is fitted to a fire service, a drop in water pressure might set off fire alarms, so make sure you tell the fire brigade and area wardens what you are doing before you begin.

4.5 Prepare the work area

As well as making the work area safe, you must also make sure it is prepared in a way that allows you to do the job well and efficiently.



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4.6 Required certification

Any person entering into a contract to test and maintain BPDs must ensure that the person doing the testing is licensed. They must also make sure local water authority and Australian Standards testing and maintenance requirements are met. In some circumstances, organisational requirements will set down more regular testing.

4.7 Quality assurance requirements

Quality assurance will depend on the particular workplace, but you must identify what is needed for programmed maintenance and make sure it will happen.

During building construction or renovation, the licensed plumber must identify what type of BPD is needed by checking the job plans and specifications. Make sure the plans have been approved by the local water authority by checking for the 75 mm square stamp on the appropriate page(s) of the working drawings.

You must also determine environmental requirements and make sure they will be met. Any hazardous chemicals or substances must be reclaimed, stored and disposed of in compliance with Environment Protection Authority (EPA) requirements.

When installation, testing and commissioning are complete, a Certificate of Compliance must be lodged with the Plumbing Industry Commission, with a copy to the building contractor (or the owner if more appropriate). You must also notify the local water authority so they can register the installation of the BPD.

Testing and inspection are then required every 12 months. We will discuss this requirement more in a later section.



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Activity 3

Based on your work experience, explain in your own words why it is important to analyse relevant drawings and specifications as you prepare for work.

What are the quality assurance requirements of your current workplace (or a recent workplace) during preparation for commissioning and maintaining BPDs?

Explain how working with an apprentice might affect your preparation.



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Activity 4

Read the following workplace scenario and complete the activity table below.

You are engaged to test and commission two BPDs already installed on a bidet in a residential dwelling. The devices are in an adjacent cupboard which is big enough to allow proper testing and commissioning. Your job is to ensure the job safety, that drains are working and discharge legally, that required job documentation is completed and that the owner/occupier knows what is required of them.

Examine each of the following planning issues. In the spaces provided, suggest how each issue may affect this workplace situation and how you would plan to deal with it.

Planning

issues

How could these affect this

site?

How will you deal with these

issues?

Occupational health and safety

Environmental requirements



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Planning

issues

How could these affect this

site?

How will you deal with these

issues?

Quality assurance

Statutory/regulatory authorities

4.8. Identifying testing and

commissioning requirements

Testing and commissioning BPDs is always a complex task. Because it must comply with the relevant standards, procedures used do not differ dramatically from job to job or location to location, but nevertheless the specifics of what you do and how depend on what you learn from a range of documents, such as job specifications, standards, authorities‘ requirements and so on. It is therefore vital that you know where to get the information you need and how to apply it.

Your main sources will be:

• regulations and other legislative requirements, particularly those pertaining to plumbing regulations, building codes, OH&S and environmental requirements

• relevant Australian Standards including AS/NZS 3500.1 Water Supply – Acceptable Solutions

• manufacturers‘ specifications and instructions

• employer requirements



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• instructions from other authorised organisational or external personnel.

You can find out about correct service/system design as well as testing and commissioning requirements from the BPD manufacturer’s maintenance manual. You can get these manuals on the Internet or in hard copy form delivered to you with the device. The relevant local water authority will have specific requirements for test reporting to document the work procedure and for quality assurance processes for your testing equipment.

As discussed earlier in this unit, once the BPD is installed and registered with the local water authority, the responsibility for meeting ongoing requirements then rests with the owner/occupier. If building ownership changes, the incoming owner/occupier has responsibility.

Find out the hazard rating

AS/NZS 3500 Table F1 sets out the hazard rating and required protection of fixtures appliances and apparatus. Check Table F2 to determine the hazard rating and required protection at the connection to the specific section of the water supply system. Table F3 helps you determine the hazard rating and required protection at the boundary of the property to protect the network utility’s water supply, or mains water, from contamination.



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Activity 5

You have been given the task of installing BPDs in a metal finishing plant. You have prepared for the work and are now at the stage where you need to obtain vital information on the service/system design, and of the requirements for testing and commissioning it.

Explain how you would do that.

Explain the type of backflow prevention devices that are likely to be used.



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5. The testing and commissioning

procedure

5.1 A basic installation

As you have already learned, installation and testing of BPDs must comply with relevant standards, job specifications, manufacturers’ recommendations and authorities’ requirements.

The following is an outline of the basic steps that would be followed in installing a double check valve (DCV). It is also a general guide to the steps for installing any testable backflow prevention device.

• Install the DCV. It must be easily accessible for periodic testing and maintenance.

• Flush all upstream piping thoroughly to remove foreign matter.

• Install the BPD. For ease of maintenance and testing, position the device horizontally and leave some clearance between its lowest part and the floor or flood grade.

• After installation, close the downstream or number 2 shutoff valve, pressurise the device and bleed air through test cock number 3. Then open number 2 shutoff valve.

Remember

The device must be tested periodically in compliance with local requirements (at least once a year, but more often if service conditions warrant).



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5.2 Basic test procedures

• Set-up for the test procedures outlined in this section is illustrated in Figure 7 that follows test no 1.

• See also section 6.7 for a checklist of common faults and remedies.

• All connections must be free from leaks in order to achieve accurate readings during testing.

Double check valve (DCV) test 1

Purpose: To test check valve #1 for tightness against reverse flow.

Requirement: The valve must allow no through-leakage in the opposite direction to normal flow under all conditions of a pressure differential.

Steps

1. Bleed water through all three test cocks to flush any foreign material.

2. Connect the ’high’ side hose to test cock #1. Connect the ‘low’ side hose to test cock #2. Open test cocks #1 and #2. Bleed both hoses, making sure to bleed the low side last.

3. Close #1 shutoff valve, then close #2 shutoff valve.

4. Slowly open bypass valve #1 and lower the pressure at test cock #1 approximately 14 kPa below the pressure at test cock #2.

Note: Check valve disc compression may make both ‘high’ and ‘low’ side gauges drop at the same rate (approximately 70 – 105 kPa or more). After the check valve disc compresses fully, you should be able to achieve the required ‘high’ side pressure of 14 kPa below the ‘low’ side.

• If this pressure differential can be maintained, you report check valve #1 as ‘tight’ or ‘okay’ and go to test 2.

• If this pressure differential cannot be maintained, go to step 6.



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5. Open #1 shutoff valve to depressurise the device.

6. Loosely attach the vent hose to test cock #1. Bleed all air from the gauge and vent hose by opening bypass valve #2. Close bypass valve #2 and tighten the vent hose. Open test cock #1. Close #1 shutoff valve.

7. Loosen the ‘low’ side hose at test cock #3 and lower the pressure in the assembly approximately 70 kPa. Retighten the hose.

8. Simultaneously open bypass valves #1 and #2 very slowly. If the check valve is holding tight, the ‘high’ side gauge will begin to drop while the ‘low’ side gauge will rise. Close both bypass valves. If a small pressure differential (no more than 35 kPa) is created and held, report the check valve as ‘tight’ or ‘okay’. If a pressure differential cannot be maintained, report the check valve as ‘leaking’.

Figure 7 – Basic test procedures



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Double check valve (DCV) test 2


Requirement: The valve must allow no through-leakage in the opposite direction to normal flow under all conditions of a pressure differential.

Steps

Same as test #1 except the ‘high’ side hose is connected to test cock #3 and the ‘low’ side connected to test cock #4. To restore normal operation, close all test cocks, remove testing equipment and open shutoff valves #1 and #2.

5.3 The reduced pressure zone device

(RPZ)

Installation

• Flush all upstream piping thoroughly to remove foreign matter first.

• Make sure the device is easily accessible for periodic testing and maintenance.

• Provide adequate drainage for the relief valve discharge. Drainage may be piped away, providing an approved air gap device is used.

• Never locate an RPZ where it may end up under pooled water.

• Install the device horizontally with enough clearance from walls and/or obstructions for testing and maintenance. Clearance between the lowest part of the device and flood grade or floor should be at least 300 mm.

• A ‘Y’ strainer can be installed just upstream of the RPZ assembly to stop debris entering the device. Debris can foul the check and/or relief valve.

• Use pipe sealant on external threads only (if applicable).

• Use wrench grips provided (if applicable).



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• On completion, and with downstream or #2 shutoff valve closed, pressurise the RPZ and bleed air through test cock #3. Then open #2 shutoff valve. (See Figure 8.)

An RPZ must be tested periodically – that is, in compliance with local Codes, but at least once a year, as service conditions warrant.

Test set-up is illustrated in Figure 8.

Reduced pressure zone device (RPZ) test 1

Purpose: To test operation of the pressure differential relief valve.

Requirement: The pressure differential relief valve must operate to maintain the ‘zone’ between the two check valves at a minimum of 14 kPa less than the supply pressure.

Steps

(See Figure 8.)

1. Bleed water through all three test cocks to flush any foreign material.

Note: Open test cock #1 very slowly to avoid accidental dumping of the relief valve.

2. Connect the ‘high’ side hose to test cock #1. Connect the ‘low’ side hose to test cock #2.

3. Open valves #1, #2 and #3.

4. Slowly open test cock #2 and bleed all air from gauge and hoses through the ‘vent’ hose. With test cock #2 held in the open position, slowly open test cock #2 and bleed all air again through the ‘vent’ hose. Close valve #2. Then close valve #1.

5. Close #2 shutoff valve.



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6. Slowly open valve #3 until the differential gauge needle starts to drop.

Note: It is important that the differential gauge needle drops slowly. Maintain #3 at this position and observe the differential pressure reading at the moment you note the first discharge from the relief valve.

7. Record this reading as the opening differential pressure of the relief valve and close valve #3.

The check valve must allow no through-leakage in the opposite direction to normal flow under all conditions of a pressure differential.



Steps

(See Figure 8.)

• Maintain the #2 shutoff valve in the closed position (from test 1).

• Loosely attach the ’vent’ hose to test cock #3.

• Bleed all air from the ’vent’ hose by opening valve #2.

• Close valve #2 and tighten hose connection to test cock #3. Then open test cock #3.

• Loosen the ’low’ side hose at test cock #2 slightly and re-establish the normal reduced pressure within the zone. Then retighten hose.

• Open valve #2. If the differential pressure remains steady, check valve #2 is reported as ’OK’. If the differential pressure falls until the relief valve opens, record check valve #2 as ’leaking’. Test 3 then cannot be completed.



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Purpose: To test the static differential pressure across check valve #1.

Requirement: The static differential pressure across check valve #1 must be at least 21 kPa more than the opening differential pressure of the relief valve as recorded in Test no 1.

Steps

1. With the testing equipment installed as set out in test 2, record the static differential pressure across check valve #1 as indicated on the gauge.

Note: The gauge needle should be steady.

2. Restore operation. Close all test cocks. Open all needle-valves. Open #2 shutoff valve and carefully remove all test equipment.

Figure 8 – Conbraco reduced pressure backflow preventer



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5.4 The pressure vacuum breaker (PVB)

Installation

The PVB must be installed where it is easily accessible for periodic field-testing and maintenance and not in a location subject to ponding or freezing. It must be at least 300 mm above the highest outlet and be ventilated to the atmosphere at all times.

Flush all upstream piping thoroughly to remove foreign matter before installation.

The pressure vacuum breaker (PVB) test 1

Purpose: To test the differential across the valve.

Step

1. Close valve 5.

2. Ensure inlet valve 4 is open.

3. Open and close test cocks to flush the system.

4. Connect a high-pressure hose to test cock 1 and a low-pressure hose to test cock 2.

5. Open test cocks 1 and 2.

6. Open high-pressure valve A and vent through valve C.

7. Close high-pressure valve A.

8. Open low-pressure valve B and vent through valve C.

9. Close low-pressure valve B.

10. Record reading (a minimum reading of 7 kPa is required for the valve to pass the test).

11. Disconnect test equipment.



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The pressure vacuum breaker (PVB) test 2

Purpose: To test the differential of the pressure vacuum breaker air inlet valve.

Steps

1. Remove the air port shield from the device.

2. Connect a high-pressure hose to test cock 2.

3. Open test cock 2 and vent through valve C.

4. Close valve C then valve 4.

5. Open valve B.

6. Record reading (reading must be at least 7 kPa for the valve to pass test 2).

7. Disconnect test equipment.

8. Replace air port shield.

5.5 Test completion

Make adjustments as needed

When testing is complete, you should always be prepared to make adjustments as needed, based on your testing. Then make sure you document everything you have done and submit your report according to regulating authorities’ requirements.

Note

Testing should take into account the full range of conditions that may impact on the device.

Document your testing

The document that follows is an example of a typical inspection and maintenance report.



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Test report

Owner/occupier: Location of device:

Address:

Contact person: Date of test:

Make: Size:

Model number: Serial number:

Individual □ Zone _ Containment □

Test results

Reduced pressure zone device Pressure vacuum

breaker

Double check valve

assembly

Relief

valve

Check

valve

Air inlet

1st check 2nd check

Initial

test

DC closed tight _

KPZ…… kPa

Leaked _

Closed tight _

Leaked _

Opened at.…… kPa

…… kPa

Leaked _

Opened at……kPa

Did not open □

Repairs

and

materials

used

Test

after

repairs

DC closed tight □

RPZ…... kPa

Closed tight □

Opened at…… kPa

…… kPa Opened at……kPa

Company name:

Certified tester:

Address: Signature:

Witness:

Signature:

License number:

Date: _ Pass _ Fail

Certificate of compliance number:

Test kit serial number: Date test kit last certified:

Place of certification:

Figure 9 – Example of typical inspection and maintenance report



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Activity 6

Read the description below of a real life project. Think about the problems that arose in that project and how you would deal with them. Then write your responses in the table below.

A cooling tower has been installed in a commercial laundry. The water supply to the cooling tower has a quick-fill valve to allow initial filling and later refilling. It has a float valve to keep a constant water level in the cooling tower reservoir. An air gap must be provided to prevent backflow and this air gap must be registered with the local water authority. The air gap must be determined by the size of the opening in the quick-fill valve, not the ball float valve (using Table 4.3 from AS/NZS 3500.1). The cooling tower needs a chemical dosage pump to minimise algae, scaling and corrosion. A hose bib is needed to help with chemical mixing and cleaning of the tower. The bib must be protected to the same rating as the cooling tower (high hazard). Annual testing (or testing as required by the local water authority) must be done by a person licensed by the Plumbing Industry Commission for backflow testing. A scheduled maintenance plan is needed to ensure proper protection of the potable (drinking) water supply. Copies of the test report must be given to the owner/occupier and the local water authority when testing is completed.

Explain how you would deal with the following situations from the above scenario.

Situations that

occur

on the job

How will you deal with

these situations?

Very high pressure and flow rate



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Situations that

occur

on the job


these situations?

Requirements for installation and testing seem unclear.

You identify some OH&S concerns.

(Dosage pump is leaking onto the roof and entering the stormwater system.)

Testing equipment seems faulty.

You need to make precise measurements.



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Situations that

occur on the job


these situations?

A fellow worker doesn’t follow directions, even after you have used voice and hand signals, two-way radio and site-specific instructions.

You see examples of faulty plumbing in the layout of the hot and cold water system.

A fellow worker is not aware of the documentation needed on job completion.



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6. Maintenance

As well as testing and commissioning, you must also be familiar with the ongoing service/maintenance requirements for BPDs. As a general rule, these requirements are determined by manufacturers’ specifications and authorities’ requirements, particularly those relating to plumbing regulations, building codes, OH&S and the environment. Sometimes, other relevant factors must be taken into account.

6.1 Meeting requirements

As you already know, AS/NZS 3500 - 4.4.6 requires testable backflow devices to be commissioned and tested after installation and before use. It also requires them to be maintained in working order and tested for this at least yearly. AS/NZS 3500.1 Water Supply – Acceptable Solutions is also relevant.

Reduced pressure zone devices, double check valve assemblies, pressure type vacuum breakers, registered break tanks and registered air gaps can only be installed when there is a defined program in place for maintenance, registration and test certification. Otherwise, where there is no such program, these devices must not be fitted and the standard air gap requirements apply.

All work must comply with manufacturers’ recommendations for the device and for individual components. Parts from different manufacturers are not interchangeable. Valves might look similar and parts from different sections of the valve might look similar, but you should never attempt to interchange these parts (springs, valve seats, etc).

During testing, the line strainer must be checked to ensure it is fitted in the right place, with the correct direction of flow and minimum clearances. These requirements must be maintained in compliance with AS/NZS 3500 Clause 4.6.3.1 and AS/NZS 2845.



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6.2 Safety

As with testing, you must follow standard operating procedures during maintenance work to minimise the risk of injury to workers and people in the immediate area.

Potential risks to the safety and health of workers and others must be minimised as far as practicable and you must notify all relevant people before any shutdown of the water supply to the area. In some instances, shutdown may have to be documented and signed off before any work starts.

6.3 Following appropriate workplace

procedures

As with testing and commissioning, you must work out who will be affected by the work and how. For example, if you are to service a device in an existing building, you must seek permission to enter and locate the device and notify the owner/occupier that the water has to be temporarily turned off. Testing a BPD requires no-flow conditions, but if a commercial or industrial operation needs uninterrupted water supply for cooling and boiler feed, etc, a ring main or parallel supply may be needed. This situation is most likely with hospitals and continuous process industries where water cannot be cut off without a planned and coordinated shutdown.

While testing is underway, trying to use water will reduce supply pressure to zero and if unprotected cross connections exist, back-siphonage might contaminate the building’s water supply. When you seek permission for shutdown, you should therefore advise the owner and/or occupiers to not use water until testing is finished and normal water supply restored.



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6.4 Quality assurance: whose

responsibility?

After testing and commissioning are completed and the Certificate of Compliance and reporting requirements have been met, quality assurance (programmed maintenance) becomes the responsibility of the building owner. As you have already learned, the local water authority registers the installation and will require inspection and testing every twelve months. The local water authority will send the owner a reminder notice before each inspection and test is due. It is then the owner’s responsibility to have the valve inspected and tested by a licensed plumber before the due date. Random audits are carried out by the local water authority on the documentation of this annual procedure.

The local fire authority and area warden (if applicable) should be notified of the maintenance work because of the possibility that a drop in water pressure might activate fire alarms.

6.5 Required certification

Any person entering into a contract to test and maintain BPDs must ensure that the person doing the testing is licensed. They must also make sure local water authority and Australian Standards testing and maintenance requirements are met. In some circumstances, organisational requirements will set down more regular testing.

6.6 The procedure

The following is a general outline of what you will be required to do as a plumber with responsibility for the maintenance of BPDs:

Step 1: Request permission from owner/occupier to enter facility.

Step 2: Obtain permission from the owner/occupier or their representative to shut down water supply.

Step 3: Advise owner/occupier not to turn on water supply during testing.

Step 4: Determine the type of device to be tested.



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Step 5: Determine the manufacturer of the device to be tested.

Step 6: Determine the direction of water flow.

Step 7: Identify test cocks and open them sequentially to flush foreign matter.

Step 8: Connect testing adapters to test cocks.

Step 9: Shut off inlet and outlet isolating valves.

Step 10: Dismantle and clean out line strainer and reassemble.

Step 11: Turn on inlet isolating valve.

Step 12: Connect test kit to appropriate test points.

Step 13: Test as required, using the appropriate procedure.

Step 14: Check replacement components using the documented procedures.

Step 15: Decide if replacement and/or repairs are needed.

Step 16: Ensure that replacement and/or repairs accord with specifications.

Note

It is recommended that you use a checklist such as the above to assist you when servicing and maintaining backflow prevention devices. The checklist helps you carry out tasks in the right order and reduce the likelihood of accidentally skipping steps.



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6.7 A checklist of common faults and

remedies

Symptom Cause Corrective action

1. Relief valve continuously discharges during no-flow condition.

No 1 check valve is fouled with debris.

Inspect and clean seat disc and seat.

No 2 check valve is fouled with debris and there is backpressure condition.


No 1 check poppet stem is not moving freely in the guide (or no 2 check poppet during a backpressure condition).

Inspect for debris or deposit on poppet stem or guide.

2. Relief valve discharges continuously during flow and no-flow conditions.

Relief valve is fouled with debris.

Inspect and clean relief valve seat disc and seat.

Damaged diaphragm (allows water to pass through from inlet to zone).

Replace diaphragm.

Sensing passage to inlet side of diaphragm plugged.

Inspect and clean passage in cover and body.

No 1 check poppet stem not moving freely in poppet guide.

Inspect for debris or deposits on poppet stem or guide.

3. Relief valve discharges intermittently in a ‘spitting’ action during no-flow condition.

Pressure fluctuations (water hammer) from supply.

Eliminate or reduce pressure fluctuations.



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4. Relief valve does not open during field test 1.

No 2 shutoff valve not closed completely.

Close no 2 shutoff valve or inspect for possible through leakage.

Test equipment improperly installed.

Recheck test procedure.

5. No 2 check valve fails to hold backpressure.

No 2 shutoff valve not closed completely.

Close no 2 shutoff valve or inspect for possible through leakage.

No 2 check valve fouled with debris.


No 2 check poppet stem not moving freely in guide.


6. Pressure differential across no 1 check valve is low during field test 3 (does not meet 3 PSID minimum).

No 1 check valve fouled with debris.


Upstream pressure fluctuations causing inaccurate gauge reading.

Eliminate pressure fluctuations.

No 1 check poppet stem not moving freely in guide.




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7. Check valve fails to hold 1 PSID.

Shut off valve not closed completely.

Close #2 shut off valve or inspect for possible through leakage.

Check valve fouled with debris.


Check poppet stem not moving freely in guide.

Inspect for debris or deposit on poppet stem or guide.

Table 2 – Checklist of common faults



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Activity 7

Based on what has been covered in this unit and from your own experience, you should already understand what is normally required with plumbing maintenance. Ongoing maintenance means more than just checking to see whether ‘things are still working’ and replacing the pieces that are no longer working satisfactorily. It also means sound preparation, a clear understanding of specifications and what can go wrong in water systems.

Ongoing maintenance requires you to:

• assess the maintenance tasks

• assess what is required and how it should be done in the most efficient way

• ensure that the water system will continue to run efficiently without breakdowns.

In the space below, explain in your own words what you think are the major factors involved in the maintenance of backflow prevention devices.



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Think about a recent job you have worked on where sound maintenance processes have produced a good result. Describe how these sound maintenance processes made a difference to the efficiency of the water system operation.

Explain the likely short-term and long-term effects of poor maintenance procedures for backflow prevention devices in water systems.

3.3 Sizing – overview



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7. Finalisation procedures

7.1 Restoring the work area

All plumbing work requires you to properly restore the work area. Because plumbing work often impacts on the environment, this aspect of your work must be addressed as part of the workflow.

Restoring the work area requires you to repair any damage to the site. For example, you might need to fill in or cover holes. If soil has been removed or moved, you will need to replace it to the natural surface level. You might need to sweep and wash down the area to restore it to its original state. If a device is located in a pit, the pit lid(s) must be replaced in a way that avoids creating a trip/fall hazard. You will also need to remove all waste materials in accordance with requirements of government and environmental authorities.

Guidance on the restoration of work areas involved in all plumbing work is provided by:

• local, state and national governments’ legislation and regulations

• Environment Protection Authority (EPA), with particular reference to hazard control and the disposal of hazardous materials and substances

• manufacturers’ recommendations and workplace procedures

• quality assurance requirements, including International Standards

• company quality assurance policies and risk management strategies

• site safety plan and workplace operations and procedures.



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7.2 Waste disposal

As with all domestic industry worksites, the removal of waste products is the responsibility of the subcontractor if the building contractor has not provided a waste removal system. Commercial and industrial worksites usually have such a system in place.

You must ensure refuse or waste material is recycled in the right way. If disposal is needed, it must be in accordance with Environment Protection Authority and local council regulations.

7.3 Restoring equipment and tools to

good working order

Tools and equipment must be removed from the site, repaired or maintained as needed and properly stored. The practice of cleaning your equipment before returning it to its allocated position in the work vehicle or the lockup site shed ensures that it is maintained in good working order. It also helps to give it a longer working life.

7.4 Documentation

You must complete all required documentation on environmental impact, recycling and/or disposal.

Activity 8

You are to test and commission a BPD located in a pit in a public thoroughfare.

What might be the outcomes if you don’t restore the work area properly when you have finished the job?



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Final assessment activity

Your final assessment in this unit will require you to test and commission two each of high, medium and low hazard backflow prevention devices, incorporating at least two different double check valves, two different pressure type vacuum breakers and two different reduced pressure zone devices.

You will also be required to indicate the ongoing maintenance requirements for each of the devices.

Throughout your assessment tasks, you will need to show you can correctly identify the location, design and details of the proposed work, correctly select and use appropriate processes, tools and equipment, work to specification and in compliance with regulations, standards and organisational quality procedures and processes.

Please refer to your assessor for precise details of your assessment tasks.

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