Plumbing, from the Latin for lead (plumbum), is the skilled trade of working with pipes, tubing and plumbing fixtures for potable water systems and the drainage of waste. Plumbing originated during the ancient civilizations such as Roman, Persian, Indian, and Chinese civilizations as they developed public baths and needed to provide potable water, and drainage of wastes. A plumber is someone who installs or repairs piping systems, plumbing fixtures and equipment such as water heaters. The plumbing industry is a basic and substantial part of every developed economy due to the need for clean water, and proper collection and transport of wastes.
Plumbing is a system of pipes and fixtures installed in a building for the distribution of potable water and the removal of waterborne wastes. Plumbing is usually distinguished from water and sewage systems, in that a plumbing system serves one building, while water and sewage systems serve a group of buildings or a city. Improvement in plumbing systems was very slow, with virtually no progress made from the time of the Roman system of aqueducts and lead pipes until the 19th century. Eventually the development of separate, underground water and sewage systems eliminated open sewage ditches and cesspools.
Plumbing equipment, not present in all systems, include, for example, water meters, pumps, expansion tanks, backflow preventers, filters, water softeners, water heaters, heat exchangers, gauges, and control systems.
Plumbing fixtures are the devices installed for the end-users. Some examples of fixtures include water closets (toilets), urinals, bidets, showers, bathtubs, lavatories, utility and kitchen sinks, drinking fountains, ice makers, humidifiers, air washers, fountains, eyewashes, floor drains, garbage disposers, and hosebibbs.
In addition to the straight pipe or tubing, many fittings are required in plumbing systems, such as valves, elbows, tees, and unions. The piping and plumbing fittings and valves articles discuss them further.
Water systems of ancient times relied on gravity for the supply of water, using pipes or channels usually made of clay, lead or stone. Present-day water-supply systems use a network of high-pressure pumps, and pipes are now made of copper, brass, plastic, steel, or other nontoxic material. Present-day drain and vent lines are made of plastic, steel, cast-iron, and lead. Special waste systems for acid waste often utilize polyvinylidene difluoride piping or boron silicate glass piping. Lead is not used in modern water-supply piping due to its toxicity.
The 'straight' sections of plumbing systems are of pipe or tube. A pipe is typically formed via casting or welding, where a tube is made through extrusion. Pipe normally has thicker walls and may be threaded or welded, where tubing is thinner-walled and requires special joining techniques such as 'soldering', 'compression fitting', 'crimping', or for plastics, 'solvent welding'.
The major categories of plumbing systems or subsystems are:
- Potable cold and hot water supply
- Traps, drains, and vents
- Septic systems
- Rainwater, surface, and subsurface water drainage
- Fuel gas piping
- Medical Gas systems including: Vacuum, Air, Medical Air, Oxygen, Nitrogen, Nitrous Oxide, and Carbon Dioxide.
- Firestopping is required where mechanical penetrants traverse fire-resistance rated wall and floor assemblies, or membranes thereof. This work is usually done worldwide by the insulation trade and/or specialty firestop sub-contractors.
Of increasing interest, for ecological reasons, are gray-water recovery and treatment systems. These systems can consist of rain water collected from the roofs or other projected areas of the structure being stored in a cistern or special retaining pond. This water can then be treated to reduce the growth of bacteria. Use of reclaimed gray-water is restricted to non-potable uses such as supplies for toilets, urinals, irrigation systems or HVAC.