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Reduced pressure zone device connected to a fire hydrant
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 assembly (RPPA).[4]
ASSE Standard 1013 - Reduced Pressure Backflow Assembly
ASSE Standard 1015 - Double Check Valve Assembly
ASSE Standard 1020 - Pressure Vacuum Breaker
ASSE Standard 1047 - Reduced Pressure Detector Assembly
ASSE Standard 1047 - Reduced Pressure Detector Assembly Type II
ASSE Standard 1048 - Double Check Detector Assembly
ASSE Standard 1048 - Double Check Detector Assembly Type II
ASSE Standard 1056 - Spill Resistant Vacuum Breaker
Backflow preventers are categorized into three groupings: Assembly, Device or Method. With the exception of elimination, these are the only ways one can control backflow from taking place.
The eight named backflow assemblies all have two resilient seated isolation/shut off valves with properly located test ports. These assemblies have the distinct advantage of being in-line serviceable and can be tested & repaired without having to remove an installed assembly. Special accredited courses are given to test & repair backflow assemblies and only certified testers may test backflow assemblies.
There are approximately fifteen devices related to backflow which cannot be tested, as they do not have isolation valves or test ports and there are no standards (test procedures) set in place to test for any device. This is what sets an assembly apart from a device. An assembly is testable, but a device is not.
Lastly, an air gap or barometric loop are methods to prevent backflow from taking place. These are also non-testable.
^"Methods and Devices for the Prevention of Backflow and Back-Siphonage" (PDF). Cross-Connection Control Manual. p. 21.
^Public Works Technical Bulletin 420-49-16: Cross-Connection Control at Army Installations(PDF). U.S. Army, Corps of Engineers. 16 July 2001. pp. 10, 12. Retrieved 23 July 2015.
^"Miami-Dade Water and Sewer Department Approved Backflow Prevention Assemblies" (PDF). Miami-Dade Water and Sewer Department. Retrieved 23 July 2015.
^Backflow Prevention Certification Workshop: Information & Materials(PDF). South Carolina Department of Health and Environmental Control. pp. 7–8. Retrieved 23 July 2015.
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