Sanitary-Plumbing
Design
Layout of fixture, spacing and height are discussed in design of wet area. This section deals with water supply and drainage.
Grading for water supply piping system
Factor | Grading criteria | Grade | ||
Size |
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Yes:5
No:1 |
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Material |
Note: use of lead, lead alloy, unlined cast iron, unlined galvanized iron, bare mild steel are prohibited in Singapore. |
Yes:5
No:1 |
||
Strength | Pipes should be strong to withstand the following pressures:
|
Yes:5
No:1 |
||
Layout | A simple layout can eliminate congestion, stagnation and contamination.
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Yes:5
No:1 |
||
Safe distance | A sufficient distance should be maintained from structure or other services running parallel for easy maintenance and to avoid interference or damage. | |||
> 400 mm: recommended. | 5 | |||
200-400 mm: acceptable under unavoidable condition. | 3 | |||
< 200mm: congestion. Direct contact should be presented by special measures. | 1 | |||
Cross connection |
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Yes:5
No:1 |
||
UG pipe protection | Underground pipes need protection from pedestrian and vehicular traffic, but at the same time should be accessible for repairs. A proper backfilling of adequate depth is mandatory.
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Yes:5
No:1
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Pipe type | Depth | |||
Mains under roadway | ≥ 1 m laid with cover | |||
Mains | ≥ 0.5 m laid with cover | |||
Service pipes | ≥ 0.2 m | |||
Protection and layout of underground pipes | ||||
UG pipe Support | Underground pipes are subjected to traffic load and settlement due to soil subsidence. Support should consider geometric dimension of trench, backfill, embedment, trench support and soil type. | |||
Continuous longitudinal support | 5 | |||
Supporting piers | 3 | |||
Nothing | 1 | |||
Above gr. pipe protection |
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Yes:5
No:1 |
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Above gr. pipe support |
Faulty pipe installation – common causes of airlock |
Yes:5
No:1 |
||
Access |
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5 | ||
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3 | |||
|
1 | |||
Pipes within walls | ||||
Noise prevention | Confined for fixed fixtures. | 5 | ||
Strong support & easy bend. | 4 | |||
Thick walled pipe, padded insulation between piping & bracket/ clip. | 3 | |||
No precaution. | 1 | |||
Joining | Joints should be watertight and able to sustain static and dynamic stress.
Reducer at joint pipes with different diameters
|
Yes:5
No:1 |
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Pipe / fitting material | Suitable joints | |||
Plastics : PVC, UPVC etc | Compression, push-fit, fusion weld, solvent weld | |||
Low carbon steel (LCS) | Compression, press-fit, threaded, disconnection. | |||
Copper | Compression, press-fit, push- fit, soldered | |||
Penetration | Penetrations are weak points and susceptible to leakage or entry of rodents.
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Yes:5
No:1 |
||
Cleaning facility | Washout or flushing facility is required for cleaning purpose.
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Yes:5
No:1 |
||
Isolation valve |
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Yes:5
No:1 |
||
Air valves | Gradient changes can collect air at summit and cause airlocks. To prevent:
|
Yes:5
No:1 |
Grading for hot water supply
Factor | Grading criteria | Grade |
Piping design | Heat loss is prevented by:
|
Yes:5
No:1 |
Material | Galvanic corrosion and fault free joints are prevented by: | |
Use of same material for the piping and fittings | 5 | |
Dissimilar metal to be kept apart by the use of adopter made of electronically non-conducting materials. | 3 | |
Non-approved material or methods to join dissimilar material. | 1 | |
Temperature control |
|
Yes:5
No:1 |
Grading for design of storage tank
Factor | Grading criteria | Grade | |
Size & strength |
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Yes:5
No:1 |
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Location |
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5 | |
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3 | ||
|
1 | ||
Material |
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Yes:5
No:1 |
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Access | Access should be easy, safe and for authorized person only. , Entry of dirt, dust, insects, birds etc should be prevented. General requirements are;
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Yes:5
No:1 |
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Water circulation
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Storage tanks are typically fitted with inlet, outlet, overflow, washout pipe and valves. The arrangement should minimize stagnation and facilitate cleaning. | Yes:5
No:1 |
|
Elements | Location | ||
Inlets | At a level higher than the overflow pipe(s). The distance between the discharge and highest overflow pipe should be at least the diameter of that overflow pipe. | ||
Outlets | At 75 – 100mm above the bottom of the tank and at the end diagonally opposite to the inlets to avoid stagnation. If two or more tanks are coupled together in series, the inlets and the outlets shall be positioned at opposite ends of the series. | ||
Overflow | At desired maximum water level. It carries excess water to sewage and thus prevents spillage and flooding. | ||
Washout | At floor level of large capacity tank (> 2300L) for cleaning. The floor of the tank shall be laid to a slight fall to the wash out pipe. | ||
Sump | Collects sediments at a depressed area and facilitates cleaning. | ||
Ventilation |
|
Yes:5
No:1 |
Grading for design of general and sewage pumps
Factor | Grading criteria | Grade |
Capacity |
|
Yes:5
No:1 |
Material | The body and parts made of strong and corrosion resistant material (e.g. cast iron or stainless steel) that doesn’t react with the pumped medium. | Yes:5
No:1 |
Housing |
|
Yes:5
No:1 |
Grading for design of sanitary appliances
Factor | Grading criteria | Grade | |
Material |
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Yes:5
No:1 |
|
Appliance fixing | Type | Fixing detail | Yes:5
No:1 |
Floor mounted | Outlet to the discharge is joined with a purpose made flexible connector (pan collar or floor flange), closet bolt or lag bolts. | ||
Wall hung | Bolts and nuts to hold an independent support frame / bracket so that no strain is transmitted to the connector or any other part of the plumbing system. | ||
Embedded in floor | E.g. squatting pan. Bedded in sand and concrete over a recessed RCC floor slab so that its parts don’t protrude below the slab. The surrounding floor is graded to drain off water into the pan. | ||
Note: Where fixture and wall meets, the part should be sealed. No fixture should be embedded in wall or supported on supply or discharge pipe work. | |||
Supply |
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Yes:5
No:1 |
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Discharge |
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Yes:5
No:1 |
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Floor waste and trap |
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Yes:5
No:1 |
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Access for cleaning |
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Yes:5
No:1 |
Grading for design of sanitary piping
Factor | Grading criteria | Grade |
System selection & venting |
|
Yes: 5
No: 1 |
Pipe design |
|
Yes: 5
No: 1 |
Layout |
|
Yes: 5
No: 1 |
Access |
|
Yes: 5
No: 1 |
Joints |
Note: If prefabricated products are available, site fabrication should be avoided. |
Yes: 5
No: 1 |
Grading for design of sewage ejector & solid diverter tank
Factor | Grading criteria | Grade |
Pit design |
|
Yes: 5
No: 1 |
Location |
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Yes: 5
No: 1 |
Access |
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Yes: 5
No: 1 |
Services |
|
Yes: 5
No: 1 |
Pumps & piping |
|
Yes: 5
No: 1 |
Grading for design of sewer drains
Factor | Grading criteria | Grade | ||||
Material | Sewers and manholes should pose chemical resistance, abrasion resistance and sufficient crushing strength. Approved materials are:
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Yes: 5
No: 1 |
||||
Joining |
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Yes: 5
No: 1 |
||||
Location | Away from any building or structure at a distance as follows: | 5 | ||||
Sewer depth (m) | ≤ 3 | > 3 and £ 5 | > 5 | |||
Min. distance (m) | 1.0 | 1.5 | 2.0 | |||
Under a structure, sewers are placed in trench made of sturdy material like RCC | 3 | |||||
Layout
|
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Yes: 5
No: 1 |
||||
Level diff | Connection detail | |||||
Nil | Shall not form acute angles with the pipes leaving away from the manholes. | |||||
< 1.5m | Tumbling bay | |||||
> 1.5m & < 6m | Backdrop connection | |||||
> 6m | Vortex drop | |||||
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