Backflow Preventer
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Definition
An assembly installed on a water service to stop non-potable water from reversing into the public supply. Common types include the reduced pressure zone (RPZ) assembly, the double check detector assembly (DCDA), and the reduced pressure detector assembly (RPDA).
Frequently Asked Questions
What is the difference between an RPZ and a DCDA?
An RPZ assembly is used where a cross-connection carries a health hazard, such as a process or makeup water line, and it discharges to atmosphere through a relief valve if either check fails. A DCDA is a double check assembly with a metered bypass, used on fire service mains so the utility can detect unauthorized use or a leak while still allowing full fire flow.
Do backflow assemblies need annual testing?
Yes. Nearly every water authority requires backflow assemblies to be tested annually by a certified backflow tester, with results filed to the utility. A failed or untested assembly can result in the service being shut off, so testing is normally folded into a utility maintenance program.
Conclusion
Backflow assemblies protect the public water supply, and their annual certification is a recurring compliance obligation rather than a one-time installation item.
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