III.

Water Supply and Drainage Systems

In developed communities, water under pressure is secured from street water mains and piped into the buildings. In other areas, water must be obtained from on-site wells or adjacent streams or lakes, in which case great care must be taken to ensure that the water is sanitary. Where available street pressure is insufficient to serve a building because of its height, equipment within the building, such as a pump that supplies a gravity tank above the roof, a pressure tank, or a booster pumping system must be installed. In hospitals and laboratories, in addition, special water systems such as distilled, demineralized (deionized), and reverse osmosis (RO) water systems are usually required. See Water Supply and Waterworks.

Drainage systems are of two basic types: sanitary and storm water. Sanitary drainage systems carry bodily and other wastes from the plumbing fixtures and appliances by gravity through a sewer to a sewage treatment facility outside the building. Sanitary drainage piping inside the building must be linked to a system of vent piping, to keep the pressures in all sections of the drainage piping equal. This prevents the siphoning or blowing of water in the traps (U-shaped dips in the piping), which in turn prevents the harmful sewer gases, which form as sewage material decomposes, from entering the building. Storm-water drainage systems carry rainwater from the roof by gravity through a sewer to a body of water or to a dry well (an area of the ground where wastewater can drain into the surrounding soil). Basement drainage usually needs to be collected in a sealed and vented pit or tank and pumped out of the basement. Hospitals and laboratories often require additional special drainage systems for removal of acid waste, radioactive waste, and infectious waste. See Sewage Disposal.