Plumbing describes the systems of pipes, fixtures, and appliances we use to move potable (drinking) water into and through our homes and buildings, heat it, use it, and safely dispose of the wastewater. The tradesman who is a trained expert in doing this work in accordance with building codes is called a plumber. Plumbing is one of the building trades.
The word comes from plumbum, the Latin word for lead, from which water pipes were originally made. Lead ceased to be used for pipework in the 1960s because of its toxicity, but may still be found in older properties.
Water usually enters the system either from a public water main via a meter, or from a private well and pressure tank. It is then conveyed under pressure to the various fixtures that need it. One main appliance is the hot water heater, after which a series of pipes usually runs in parallel with the cold water pipes.
At the fixtures we are able to use the hot and cold water, for washing, bathing, irrigation, and sanitation. Each of these fixtures, with the exception of irrigation, also feature a connection to the drain, waste, and vent piping system (DWV). The DWV plumbing safely directs the soiled water to a public sewer line or a private septic system, while providing safe ventilation for sewer gases and to prevent siphoning of the traps, which are water filled joints that prevent sewer gases from entering the building. The water used in irrigation simply returns to the environment directly.
If a building uses a hot water or steam heating system, while it is connected to the fresh water supply, it is basically a closed system. It is also installed and maintained by plumbers.