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A backflow prevention device is used to protect potable water supplies from contamination or pollution due to backflow. In water distribution systems, water is normally maintained at a significant pressure to enable water to flow from the tap, shower, or other fixture. Water pressure may fail or be reduced when a water main bursts, pipes freeze ...
It is usually constructed of brass and resembles a 90-degree elbow with a hood on its top to allow air to enter the water system if a siphon attempts to form. Inside this elbow is a poppet valve that is held "up" by the water pressure found in the system, closing the air entrance to the device. If the pressure in the "upstream side" is reduced ...
A reduced pressure zone device (RPZD, RPZ, or RPZ valve) is a type of backflow prevention device used to protect water supplies from contamination. RPZDs may also be known as reduced pressure principle (RP), reduced pressure principle backflow prevention devices, [1] [2] reduced pressure zone assemblies (RPZA), [3] or reduced pressure principle ...
A vacuum breaker is a device that prevents water from being siphoned backward in a direction it is not desired to go. They are commonly placed on a bibcock valve or toilet or urinal flush valve, in which application they can prevent hose or drainage water from back-siphoning into the public drinking water system. This prevents contamination ...
A pressure vacuum breaker (PVB) is a type of backflow prevention device, used to keep non-potable (or contaminated) water from entering the water supply. A PVB is similar to an atmospheric vacuum breaker (AVB), except that the PVB contains a spring-loaded poppet. This makes it acceptable for applications that are high hazard or where valves are ...
Backflow occurs for one of two reasons, either back pressure or back siphonage. [1] Back pressure is the result of a higher pressure in the system than in its supply, i.e. the system pressure has been increased by some means. This may occur in unvented heating systems, where thermal expansion increases the pressure.