Plumbing

I

Introduction

Plumbing, system of piping that carries water into and out of a building. To protect public health, every inhabited building must have a supply of safe water for drinking and for the operation of the plumbing fixtures and appliances, and a sanitary drainage system for wastewater disposal. To provide the sanitary facilities required, local government authorities are responsible for establishing regulations known as plumbing codes, which govern design and installation requirements and the minimum number of fixtures needed, based on building use and the number of occupants.

II

History

The word plumbing is derived from plumbum, Latin for the metallic element lead, the material most often used for ducts and piping until it was superseded by cast iron in the 19th century. Archaeologists have found evidence of systems for disposal of human waste in dwellings 10,000 years old. Waste disposal and running water were commonly incorporated in the palaces of royalty and priests as early as the time of the Indus Valley civilization (about 2500 to 1700 bc), and these systems were well developed during the Roman Empire. Plumbing was a firmly established feature in dwellings of even the less affluent by the end of the 19th century.

Today at least 26 different systems are included in plumbing design, although not all are found in any one building. Basic modern plumbing fixtures include toilets, urinals, sinks, bathtubs, showers, laundry tubs, and drinking fountains. In addition, hospitals, laboratories, and industrial buildings require many specialized types of fixtures. Appliances that are connected to a plumbing system include dishwashers and laundry washers. Most of these fixtures and appliances require both hot and cold water. Hot water can be generated by heaters using gas, electricity, boiler water, oil, steam, or solar energy. Fixtures today are made of impervious materials such as vitreous china, enameled cast iron or steel, stainless steel, and plastic. Piping materials include cast iron, steel, brass, copper, stainless steel, aluminum, plastic, vitrified clay (tile), and concrete.

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.

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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.

IV

Safety Devices and Special Systems

Both water supply and drainage systems must be carefully designed to prevent serious contamination of the water and to stop sewer gas from entering the building. All water connections to fixtures and appliances must be provided with devices that prevent contaminants from being siphoned or forced back into the water piping, a condition known as backflow or back siphonage. Temperature and pressure-relief valves must be installed on all water heaters to prevent explosion in the event of malfunctioning controls.