Case 1

Good Practices

The Home Improvement Programme (HIP) offers residents essential and optional improvements to improve the internal living environment and address some of the common maintenance issues in older flats. Essential improvements, which are fully funded by the Government for Singapore citizen households, are necessary for public health, safety or technical reasons. They include the replacement of cast iron soil/waste pipes, spalling concrete repair, and replacement of existing pipe sockets with new clothes-drying racks. Optional improvements include toilet upgrading as well as the replacement of entrance door/gate and refuse hopper, where residents need pay only for the items they have chosen at a highly subsidised rate.

As cast iron pipes can corrode over time, they are replaced with unplasticised polyvinyl chloride pipes under the HIP.

Plumbing

Design

Pipe failure is a cumulative effect of various pipe-intrinsic (material, diameter, age), operational (corrosion, pressure) and environmental factors (rainfall, soil conditions and external stresses) acting on them. Factors attributed to pipe failure can also be classified into hydraulic or non-hydraulic factors. Specify materials that are resistant to corrosion and non-reactive to the conveyed water and surrounding ground in accordance with BS EN 545, BS EN 598 or equivalent, and that do not impart any taste or toxicity to the water in accordance with SS 375-1 or equivalent. Use of a single material for the entire system is preferable for easy connection/jointing. Specify pipe system material that does not react with the pumped
medium. The top 3 water pipe materials are: (1) Copper — durable; with antibacterial properties; good conductor of heat and hence ideal as hot water pipes, (2) Stainless Steel — durable; resistant to corrosion;
non-toxic; ideal as drinking water pipes, and (3) Plastic (UPVC, PPR, PVC, PE, PP) — durable; resistant
to corrosion and chemical.

Construction

Since the 1980s, PUB has systematically replaced older, unlined iron pipes with cement-lined ductile iron and steel pipes. In addition, the exterior of these pipes is coated with bitumen. With the pipes’ interiors lined with cement, the metal is shielded and thus reduces the occurrence of internal corrosion. The fibreglass wraps are applied to the pipe enamel to produce a more uniform coating, allow a thicker application of enamel, and enhance the coating strength. The bitumen coating with two layers of fibreglass protects the external surface of the pipe from corrosion. Pipe penetrations and joints should strictly adopt the manufacturer’s instructions. Jointing material should not enter the pipe. Caulking
at the penetration sleeve should be made watertight. Proper installation should be fulfilled while ensuring that the protective coating is not lost/damaged during installation in accordance with BS 8558, SS 636 or equivalent. Non-metallic fittings shall comply with SS 375 or BS 6290. Metallic fittings shall comply with AS/NZS 4020.

• Care should be taken to prevent causing damages during transporting, handing and installation as,
• Each element should be packed to prevent accidental damage due to impact and abrasion when transporting
• All pipes should be stored under shelter to prevent damage from rain
• Protective coating should not be damaged during lifting the pipes
• Adequate protective coating or suitable paint systems should be applied over the surface to minimize corrosion after installation.

Materials

• Provide all ferrous metal components with protection against corrosion and, if not supplied with an adequate protective coating, paint with suitable material (9-10).
• It is good practice to use plastic pipes to minimize corrosion and subsequent joint leakages in drainage pipe system.
• Care should be taken to prevent causing damages during transportation, handling and installation as:
  • Each element should be packed to prevent accidental damage due to impact and abrasion when transporting
  • All pipes should be stored under shelter to prevent damage from rain
  • Protective coating should not be damaged during lifting the pipes
  • Adequate protective coating or suitable paint systems should be applied over the surface to minimize corrosion after installation.

Quality Control

• When all the pipe work is completed, introduce a full pressure test on the pipe work to ensure that there are no leaks from the joints before starting to use or embedded into the concrete.