12 drainage
TRANSCRIPT
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RECO1006 Construction II
Drainage System
Edward CY YIUDepartment of Real Estate and Construction
January 2007
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Learning Objectives• Design of Drainage System
– Sanitary Fitments– Above ground drainage systems
• One-pipe and two-pipe systems• Drainage Installation Requirements• Drainage systems for soil, waste, rain water and grease• Vent pipe and anti-siphonage system
– Below ground (Sewage) drainage systems• Manholes and last manhole• Vent
• Maintenance of Drainage System– Survey– Repair
• Links– Buildings Ordinance, Laws of Hong Kong Chapter 123 http://www.justice.gov.hk/
• CAP 123I: Building (Standards of Sanitary Fitments, Plumbing, Drainage Works and Latrines) Regulations
• Guidelines on Maintenance and Repair of Drainage System and Sanitary Fitments– Drainage Services Department (DSD), Hong Kong http://www.info.gov.hk/dsd/
• Flood prevention • Sewage strategy and facilities
– Environmental Protection Department (EPD), Hong Kong http://www.infor.gov/hk/epd/
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Sewerage[1] Capacity• “Everyday, the people of Hong Kong produce some 2.6
million cubic metres of sewage, enough to fill up more than 1,400 Olympic-size swimming pools.
• This sewerage system includes a sewerage network of over 1,525 kilometres in total length and around 260 plants ranging from preliminary treatment (screening) plants to secondary treatment (biological) plants treating sewage from residential, commercial and industrial premises in the territory prior to disposal to the sea for dilution and dispersion through submarine outfalls.”
http://www.dsd.gov.hk/sewerage/sewerage_strategy/index.htm
[1] Drainage and Sewerage Systems refers to liquid waste disposal systems, solid waste disposal will be separately discussed.
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Authority
• Building (Standards of Sanitary Fitments, Plumbing, Drainage Works and Latrines) Regulations [B(SSF)R]
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Building Services Framework
Water in – Plumbing System Water out – Drainage System
Energy out - OTTV
Waste out – Waste Disposal System
Air in – MVAC System
Energy in – Electricity Supply Systems
People / Goods in – Transportation System (Lifts and Escalators)
Air Out – MVAC System
Fire in – Gas Supply System Fire out – Fire Safety System
People out – Transportation System
Light in – Lighting System
Sound in – Acoustics System
Light out – Lighting System (blinds)
Sound out – Acoustics System
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Drainage ConnectionsPlumbing system
Faucet
Above ground drainage system
Underground drainage system Sewerage
system
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Sanitary Fitments
• Water Closet (W.C.)• Urinals• Basins• Bath Tubs• Showers• Sinks
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Disabled Toilet
Source: BD (1997) Design Manual - Barrier Free Access http://www.bd.gov.hk/english/documents/code/BFA-E07.pdf
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Nos. of Sanitary Fitments
• Males to Females Ratio
It is recommended that the ratio of male person to female person be taken – as 1:1 for office accommodation. – as 1:1.25 for places of public
entertainment and cinemas– see table for shopping arcades,
and department stores.
• in the assessment of populations for the provision of sanitary fitments for both male and female persons
PNAP 297 and B(SSF)R s5(5)(c), 6(3)(b) and 7(3)(b)
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Nos. of Sanitary Fitments (Cont’d)
PNAP 297 and B(SSF)R s5(5)(c), 6(3)(b) and 7(3)(b)
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Types of Vertical Drainage Stacks
• Waste pipe (WP)• Soil pipe (SP)• Vent pipe (VP)• Rainwater pipe (RWP)• A/C condensation drainage pipe
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One-pipe System
• Soil and waste fittings are discharged into one common stack, with a common vent pipe.
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One-pipe Sys
Vent pipe
S&W Stack
WC
Floor drain (toilet)
Basin
Bath
sink
Floor drain (kitchen) NOT SHOWN
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Two-pipe System
• Soil and waste stacks are separately provided, with its own vent.
• Advantages?
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2-pipe system
Soil stack
Vent pipe for soil stack
Waste stackExternal u-traps
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Vent Pipe (VP) –for what purposes?
Soil and Waste Pipe (S&WP) in a One-pipe System
Sufficient fall
Cleaning eye
Rain Water Pipe (RWP)
One-pipe Drainage System in an Ageing Building Elevation
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Vent Pipe
• preventing loss of water seals in traps;
• is up to a height > 1m above roof;
• Covered with a wire cage 馬騮頭.
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Provision of Cleaning Eye
Cleaning eye
How to indicate drainage arrangement on a plan?
Find one example yourself
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Two-pipe System, Hoppers for Waste Stack, Stacks on External Wall
• A common arrangement of piping in ageing buildings in Hong Kong;
• Pros and Cons?• Any vent pipe for
waste stack?• Is it still allowed for
new developments, why?
Hopper Soil StackVP
Waste Stack
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Traps
S-Trap
P-Trap
Bottle-Trap
(Anti-siphonage – how?)
Require minimum water seal of
•50mm (for soil fitments) and
•40mm (for waste fitments)
Why trap?
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Functions of a Trap
•SARS is the result of lacking water in the U-traps of the drainage system?!
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Proposed New Traps• Why lossing water seal in traps?
– Self-siphonage where the discharge of waste water created a partial vacuum in the branch pipe thereby ‘drag’ the water in the trap away.
– Induced siphonage where the water running down the stacks created a partial vacuum behind it thereby ‘drag’ the water in the trap away.
– Compression or back pressure occurred at the lowest floors where the stack change direction.
– Natural evaporation.• How to prevent?
– Anti-siphonage pipes and traps– Back-filling arrangement (figure)– W-trap (being trying by the HKHA)– Self-refilling function
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Why U-traps are missing?Source: http://www.bd.gov.hk/english/documents/code/dsg/DrainagePipeMaintenance.pdf
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Floor drain
Shower tray
50AFFL
200AFFL
External U-Trap
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Materials of Above Ground Drainage Pipe
• S.44 B(SSF)R– Cast iron or approved– True bore, smooth
internal surface and impervious
– Protected against rust
– Galvanized mild steel– UPVC (Unplasticised
Polyvinyl Chloride)
Why UPVC is nowadays the most common used one?
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PNAPs• PNAP 157 - Test of Drain (BSSF,P,DW&L)R
73)– Cert on completion of drain test is required w/in 7
days of drain test (What is the test?)– BD may not attend the test
• PNAP 211 - Planning and Design of Drainage Works – BO 28(1) : all common underground drains shall run
in COMMON AREA or alternative provisions made for easy access
• PNAP 238 - Disposal of A/C condensation – required to indicate on plan
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Underground Drainage• Authority: Water Pollution Control Ordinance• Departments: Environmental Protection Department • requiring that all waste water produced from the
premises be conveyed to a specified location, the terminal manhole, for connection to the public sewer when one is available.
• It is an offence not to comply with the requirements in a notice. The maximum penalty is a fine of $100,000 and a daily fine of $5,000 if the offence is proved to be continued.
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Acceptance Test(s) of Drainage System
• Water test (the most commonly used for underground drains in HK)– Temporarily seal ends of drains and connections with
approved plugs;– Fill system with water to produce 1.5m head at high
end;– Allow for initial absorption;– Loss of water over 30 minutes to be measured by
adding water at 10 minutes intervals;
• Air test• Smoke test
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Petrol Interceptor• EPD PN 5/93,
PNAP 124 -Petro-interceptor (BSSF)R 90)
– Assume flatted factory will discharge noxious effluent, no connection to storm-water drainage
– Servicing and parking of vehicles requires petrol interceptor
http://www.epd.gov.hk/epd/english/resources_pub/publications/files/pn93_5.pdf
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Grease Trap
• EPD PN 5/93 –Grease Trap (BSSF)R 90)
http://www.epd.gov.hk/epd/english/resources_pub/publications/files/pn93_5.pdf
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Systems of Underground Drainage
• Separate system:– Foul water (soil and waste water) -> foul sewer– Rainwater/surface water -> storm water sewer
• Combined system:– Foul water and rainwater are drained to the foul sewer
Source of figure: http://www.winnipeg.ca/WaterAndWaste/sewage/systemOperation.stm
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Materials and Size of Underground Drainage Pipe
• Drainage pipes shall have a minimum diameter of 150mm and be of the following materials or other materials approved by DSD :-
– (i) Foul sewer - vitrified clay, ductile iron, uPVC
– (ii) Storm water drain - concrete, ductile iron, uPVC
• Foul sewers should be designed so that the velocity of the flow will exceed the self-cleansing velocityon a regular basis.
• As a general guide, the minimum fall of foul sewers is as follows :-
Source: B(SSF)R and Works Bureau (2000) Practitioner's Guidelines on Drainage Connection, Revision (April 2000)
1:100225
1:150300
1:70150
1:40100
FallDiameter (mm)
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Manholes• S.49, s.55 B(SSF)R requires manhole provision
when– Change in direction >45 degree– Change in gradient – Interval > 60m
• S.56 B(SSF)R– 215 thick brickwork in cement mortar or– 125 thick 1:2:4 reinforced concrete or other approved– Benching 1:2– Inside surface cement rendered– Cast iron cover (double-sealed airtight cover if inside
or under a building)
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Manhole Plan
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Manhole Standard Drws
Source: DSD standard drws
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Terminal Manhole
• Characteristics:– Trapped– Rodding arm
for cleaning– Opening for
FAI– Steps for
maintenance
Source: DSD standard drws
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FAI for Terminal Manhole
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Double-sealed Airtight Cover
Source: DSD standard drws
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Back Inlet Trapped
Gully (B.I.T.G)
Source: http://www.geberit.co.uk/geberit/inet/uk/wcmsuk.nsf/Pages/serv-clau-1
Use of BITG for collection of surface water and connection to foul water drain (combined system).
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Maintenance of Drainage System• Lack of maintenance resulted in tragedies
– Kwun Lung Lau landslip on 23 July 1994– See Report on the Kwun Lung Lau Landslide of 23 July 1994
(2000), 365 p. (by N.R. Morgenstern & Geotechnical Engineering Office)
• Survey– Water leakage detection system
• Maintenance– High pressure water jetting for cleansing– Annual CCTV inspection– Buildings Department’s Guidelines
• Repair– Sewer rehabilitation technology– In-situ internal lining method
http://www.bd.gov.hk/english/documents/code/dsg/Drainage-System-Guideline-Eng.PDF
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Water Leakage Detection System
• For Pressurized Services– Visual inspection– Pipe locator survey (Sonde Method)– Leak Noise Correlation (LNC)– Direct / Surface Sounding– Hydrogen Leak Detection– Aqualog 80 Leak Localization
• For non-pressurized services– Manhole survey– CCTV inspection– Man Entry Inspection– AMS-4 Leak Detection (Sonde Method)
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In-situ internal lining method
• Trenchless Drain Liner
Source: http://www.c-products.com.hk/LandUtilities/CCTV.htm
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References• Video Presentation:
– "Simplified drainage systems for large buildings" [8.5 min.] [AV 628.4 S61] • Books:
– Barry, R. (1996) The Construction of Buildings, Blackwell Science, London [690 B281]– Burberry, P. (1997) Environment and Services, Addison Wesley Longman, Essex [696
B94]– Chadderton, D. V., 2000. Building Services Engineering, 3rd ed., Chps. 7-9, E & FN
Spon, London & New York. [696 C43]– Hall, F., 1994. Plumbing, Cold Water Supplies, Drainage and Sanitation, 3rd ed., Chps.
5-9, Longman Scientific & Technical, Essex. [696.1 H17 p] – Hall, F. (1995) Essential Building Services and Equipment, Newes, Oxford [696 H17e]– Morgenstern, N.R. and Geotechnical Engineering Office (2000) Report on the Kwun
Lung Lau Landslide of 23 July 1994, Hong Kong Government, Hong Kong. • Codes of Practice:
– British Standards Institution (1978) BS5572: 1978, Code of Practice for Sanitary Pipework, BSI, UK.
– British Standards Institution (1985) BS8301: 1985, Code of Practice for Building Drainage, BSI, UK.
– Buildings Department (2005) Guidelines on Maintenance and Repair of Drainage System and Sanitary Fitments (1 page guidelines), Hong Kong Government, Hong Kong.
– Buildings Department (2004) What you need to know about Drainage Maintenance (1 page guidelines), Hong Kong Government, Hong Kong.
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The End
For enquiries, please send email to Edward CY YIU
Department of Real Estate and ConstructionThe University of Hong Kong