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Backflow is a term in plumbing for an unwanted flow of water in the reverse direction. [1] It can be a serious health risk for the contamination of potable water supplies with foul water . In the most obvious case, a toilet flush cistern and its water supply must be isolated from the toilet bowl.
Water cannot flow from the sink to the tap in normal circumstances, even if the water supply loses pressure. An air gap , as related to the plumbing trade, is the unobstructed vertical space between the water outlet and the flood level of a fixture . [ 1 ]
Backflow prevention device. The simplest, most reliable way to provide backflow prevention is to provide an air gap.An air gap is simply an open vertical space between any device that connects to a plumbing system (like a valve or faucet) and any place where contaminated water can collect or pool.
Non-return or check valves allow the free flow of a fluid in one direction but prevent its flow in a reverse direction. They are often seen in drainage or sewage systems but may also be used in pressurized systems. Valves are available in several types, based on design and purpose: Gate, plug, or ball valves – Isolation; Globe valve ...
In the U.S., every plumbing fixture must also be coupled to the system's vent piping. [1] Without a vent, negative pressure from water leaving the system can slow flow (resulting in clogs) or cause a siphon to empty a trap. The high point of the vent system (the top of its "soil stack") must be open to the exterior at atmospheric pressure.
Back siphonage is not to be confused with backflow; which is the reversed flow of water from the outlet end to the supply end caused by pressure occurring at the outlet end. [51] Also, building codes usually demand a check valve where the water supply enters a building to prevent backflow into the drinking water system.
A receptacle tester being used to check for some types of improper wiring of an outlet. For this particular tester, proper wiring is indicated by the two yellow lights. The outlet tester checks that each contact in the outlet appears to be connected to the correct wire in the building's electrical wiring. It can identify several common wiring ...
In domestic applications, traps are typically U, S, Q, or J-shaped pipe located below or within a plumbing fixture.An S-shaped trap is also known as an S-bend.It was invented by Alexander Cumming in 1775 but became known as the U-bend following the introduction of the U-shaped trap by Thomas Crapper in 1880.