Understanding Plumbing
Sinks, bathtubs, showers, laundry tubs, and bidets are connected to both the hot and cold water lines and the drain-waste-vent piping. Such fixtures are designed to be convenient and easy to clean. They are available in a variety of styles and colors. Plumbing is also connected to a variety of appliances, such as dishwashers, washing machines, drinking fountains, humidifiers, and icemakers. In addition, most buildings have outside faucets called hose bibbs to which garden hoses can be connected.
The flow of water into such fixtures as sinks, bathtubs, and showers is controlled by a faucet. Often separate faucet handles and in some cases separate faucets are installed for hot and cold water. Turning the handles of the faucets controls the flow of water.
Fixtures are also connected to the drainage piping. A U-shaped pipe called a trap is installed between the fixture and the drainage piping to prevent sewer gas from entering the building. This is accomplished automatically because some of the water leaving the fixture remains in the bend of the U and creates a water seal.
Toilets are connected to the cold-water supply and wastewater piping. Most residential structures have tank-type toilets. The tank is necessary to supply enough water in a short period of time to flush the toilet bowl. The water that is held in the toilet bowl serves two purposes: it helps keep the bowl clean, and it produces a seal that prevents sewer gas from entering the building. When the flush valve is opened, the water from the tank rushes through an opening in the tank into the toilet bowl, forcing the water and waste in the bowl through a passageway into the waste piping below. The passageway siphons, or draws off, nearly all of the water from the bowl. As the tank empties, air is drawn into the bowl, breaking the siphon action. At this time, the stopper, or flush ball, on the flush valve settles back down on the tank opening and the tank begins to refill.
The four major hazards posed by improperly installed or malfunctioning plumbing systems are leaking pipes or fixtures, entrance of sewer gas into the building, blocked waste piping, and cross-connections. Leaking pipes or fixtures can cause flooding and water damage. Leaks are caused by many things, but the most common causes for leaks are deteriorated, cracked, or broken piping or fixtures.
Sewer gas has an unpleasant odor and contains methane, which burns readily. High concentrations of sewer gas can pose a health and fire hazard. To prevent sewer gas from entering buildings, traps are installed at each inlet to the waste piping. Also, vents are extended through the roof of the building to allow excess sewer gas to escape. These vents remain open to prevent pressure from building up in the sewer system and thereby forcing sewer gas through the water seal in the traps.
Clogged waste piping can cause drains to overflow and create the same problems as those posed by leaking pipes. Generally, clogs are caused by large objects entering the waste piping or by the accumulation of solids inside horizontal waste pipes. To prevent clogs, the plumbing system should only be used as it was intended. Sometimes tree roots break through the building sewer and cause a blockage. This can be prevented by placing large trees well away from the building sewer.
The drain-waste-vent (DWV) system carries away wastewater. The DWV piping connects to the building drain, which carries the wastewater to the sewer main. The sewer main extends to the sewage treatment plant, where the wastewater is treated and released. Every fixture in a building is connected to the DWV system. Any pipe that connects to a toilet is known as a waste, or soil, pipe. Pipes that carry only liquid waste – from fixtures such as sinks and bathtubs, for example – are called drain pipes. Pipes that carry neither liquid nor solid waste and permit air to enter the DWV system are called vents. Vents extend through the roof and are open so that sewer gases can escape and air can enter. Hospitals, laboratories, automotive repair shops, photography processing plants, and dentists’ offices are among the facilities that require special DWV systems because they may discharge flammable or toxic materials into the drainage system. Such installations may have grease separators, acid neutralizing tanks, and other devices that prevent hazardous materials from entering the sewers, and they may have special air-cleaning devices installed on the vents. Also, the drains may be made from special glass piping that is resistant to the destructive action of corrosive materials.
