Frequently Asked Questions


Backflow Testing Frequently Asked Questions

1) Why do I need my “Backflow Prevention Assembly” tested annually?
a. Backflow Prevention Assemblies and Devices break or wearout, just like the parts of a car. Backflow is the hydraulic condition that can cause an RP to stop working in the described normal flow pattern.

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2) Why have I never had to test my Backflow before?
a. When your Backflow was installed it was tested prior to plumbing inspection, but because of the volume of Backflow preventers being installed and the large number of existing Backflow preventers in various lower mainland cities it is not easy for municipalities to keep you informed of when your Backflow is due to be tested. However, due to increased awareness of the importance of protecting our water many cities are taking better steps to inform people when their annual test is due.

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3) What is a Backflow preventer?
a. A Backflow preventer is a means of mechanism to prevent Backflow. The basic means of preventing Backflow is an air gap, which either eliminated a cross-connectionor provides a barrier to Backflow.

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4) What is a reduced principle (RP) assembly?
a. An RP is a mechanical Backflow preventer that consists of two independently acting, spring-loaded check valves with a hydraulically operating, mechanically independent, spring-loaded pressure differential relief valve between the check valves and below the first check valve.

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5) What is Backsiphonage?
a. Backsiphonageis a condition that causes a sub-atmospheric pressure to be applied to the upstream side of the assembly.

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6) What is an air gap?
a. An air gap is a vertical, physical separation between the end of a water supply outlet and the flood-level rim of a receiving vessel.

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7) What is a double check valve assembly?
a. A DCVA is a mechanical Backflow preventer that consists of two independently acting, spring-loaded check valves. It includes shutoff valves at each end of the assembly and is equipped with test cocks. A DC is effective against back pressure Backflow and backsiphonage but should be used to isolate only non- health hazards.

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