A domestic water system is a piped system for the purposes of conveying a portable water supply from the supplier to the end user. These systems are designed and installed to serve any type of commercial, residential, institutional or educational structure, whether a hospital, school, industry, manufacturing process or residence. The systems are required to deliver clean, safe, potable water to each point of domestic water connection and also provide a means of connecting to unsafe sources of contamination for process water use, through the use of backflow preventers or other approved means. Domestic water systems are restricted to the supply side of the plumbing system. Sanitary, drainage, waste and vent systems are physically isolated from the supply side through the use of approved air gaps, air breaks and backflow preventers in order to physically isolate and enforce this separation between the supply & waste systems.
Cold water supply
Most modern western water systems are directly fed from a municipal water system by a high-pressure pipe, usually located under the road or street. Many houses still use a cistern or a well where a convenient water system supply is not available; they commonly use a pump and pressure tank to maintain system pressure. Older houses (or houses that need gravity fed cold water, i.e. for a power shower) may also have a cold water tank. In such a case, drinking water (usually the kitchen tap) is usually fed directly from the main water supply due to the risk of contamination in the cold water tank.
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The supply may or may not be metered. Non-metered supplies are usually billed based on the size of the house (making assumptions about the number of people living in the house). However, such accommodations are increasingly rare.
The domestic water system forms a cycle consisting of the water supplies, internal distribution system, and waste/sewage removal.
Water Supplies
Depending on preference, location restrictions/oppurtunities and expense considerations, the source of water supplied to a building can vary greatly. Many homes are connected to a metered municipal water system, which forms the entire domestic water cycle outside of the internal Distribution system. Homes further from cities and other populated areas must form the entire cycle independently. In these latter cases, the water supply can be from wells, tapped springs or rivers, even rainwater storage. Whatever the supply, the water is almost alawys connected to the home at a single point.
Internal Distribution System
The internal water distribution system forms part of the cycle. Supply water enters from the munincipal supply or, for buildings not connected with a munincipal system, another form of water supply. This supply water is piped to various taps, fixtures, and appliances. The drainage from these taps, fixtures, and appliances exit through the sewage drain system.
Cold Water Supply System
Any external water supply is almost always a cold water supply. The Cold water supply system may include filter or water softner appliances and fixtures. This cold water is then fed to other fixtures, taps, and appliances that require cold water, such as sinks, hot water heaters, faucets, bathtubs, showers, toiletts, etc.
Hot Water Supply System
Domestic hot water is provided by means of water heaters, appliances intended to provide a hot water supply by heating a volume of water supplied by the Cold water supply system. The hot water from these systems is then piped to the various fixtures, taps, and appliances that require hot water, such as sinks, bathtubs, showers, washing machines, etc.
Taps, Fixtures, and Appliances
Everything in a building that uses water falls under one of the categories; Tap, Fixture, or Appliance. These devices all serve some function in the home, or they wouldn't exist. They are the loads on the system. By performing their function, most produce some form of waste/sewage which is removed by the Sewage Drain System.
Taps are water outlets without an accompanying fixture.