There are two types of plumbing systems in Singapore residential. One is the water supply system supplying drinking water and the other is drainage or sanitary system disposing of used water.
Water Supply System
Drinking water enters a home through a main water pipe. In Singapore, drinking water is provided by Public Utilities Board (PUB), a statutory board under the Ministry. The drinking water passes through a PUB water meter that registers the amount of water used by the household.
The main water pipe splits to a branch pipe to join to a water heater and form a hot water branch pipe. Both hot water and drinking water pipes bring water supply to fixtures and appliances throughout the house. Fixtures include sinks, showers, bath tubs, toilet bowls, urinals and external silcocks( extended pipe). Appliances include water heaters, washing machines and dish washers.
Sanitary or Drainage System
Used water then enters the drainage system. It must first flow past a water trap (bottle trap, toilet in-built trap, floor trap, gully trap, intercepting trap and grease trap) to trap debris in standing water and preventing sewer gas from flowing back up the drainage pipe. Every fixture must have a water trap to keep the place odour free and hygienic. The drain system works entirely by gravity, allowing used water to flow downhill through a series of large‑diameter pipes. These drain pipes are attached to a venting system or plumbing vents, consists of a number of pipes. Vent pipes bring air into the drain system to regulate air pressures, allowing the trap to hold used water and release sewer gases outside the house, usually through the roof.