3. Water Service and Components

Potable Water Supply

Potable water supply systems transport water, under pressure, that is clean, fresh and safe for human consumption. A potable water system for domestic service would consist of:

• Water Service piping that carries water from the city main or private well or other water source to the building foundation.
• Water Distribution piping or tubing that transports clean water to fixtures inside the building (this includes hot and cold water lines).

In most areas served by a city water main, potable water is treated with disinfectant or antibacterial agents (e.g., chlorine) to safeguard the health of water consumers.

Piping and tubing for potable water systems must be strong and resistant to corrosion. It must be strong to withstand internal pressures of water and external pressures when buried underground. It must resist the corrosive effects of soil and the free oxygen present in water that is very destructive to steel and galvanized iron pipe, fittings and components. Heat will also reduce the strength or pressure rating of most plastic pipe and tubing, although some plastics are rated for domestic hot water supply. Not all plastic pipes are rated for hot water service or for potable water.

One of the most important characteristics of a potable water system is that it should remain sealed to the outside environment. To maintain even pressures, consistent flows and, most important, to avoid contamination of the water, piping must beleak-proof and very durable. The materials used to make piping, tubing and components and the way in which connections are formed, are both designed to maintain the purity of the water and the consistency of supply at fixtures. The piping must only contain and transport the water; it must never add anything to the water.

Originally, domestic potable water supply systems were made from galvanized and brass piping and fittings. But steel piping was highly susceptible to corrosion while brass was too costly, also the cost of labour to install both piping systems were high. The two were rapidly replaced by copper tubing, which was far more durable and had fewer problems with scale build-up. With advances in the plastics industry, plastic tubing is increasingly found in potable water supply systems.

See Division B, Notes: Table A.2.2.5., 2.2.6. and 2.2.7. Summary of Pipe and Fittings Applications.