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My Backflow Preventer failed inspection, but what does that even mean?

I will try to explain this, Each University of Southern California Approved backflow preventer has gone through extensive laboratory testing to insure that the assemblies will protect the water supply. These approved backflow prevention assemblies must maintain specific parameters that are testable and verifiable with a differential pressure gauge. The backflow inspector is testing the backflow prevention assembly to verify that the backflow preventer is performing to the minimum standards of the function tests.

For Instance,

The Reduced Pressure Assembly must have the First Check Valve hold tight at or above 5.0 PSI. The Relief Valve must begin to discharge water at or above 2.0 PSI. The Second Check Valve must hold tight at above the relief valve opening point.

Yes, the water supply needs to be interrupted briefly to inspect the function of the backflow preventer.

The Backflow Inspector may also be looking at the backflow installation to see if it is installed according to manufacture specifications. The Reduced Pressure Backflow Prevention Assembly must be Installed 12” above Grade and have 6”to 12” of clearance for service and inspection access. The RP must never be installed below grade or in a flood plane. Most of the RP models are designed to be installed horizontally, in the unusual case that they may be vertically installed it is normally approved for flow up not flow down.

Ok, it failed! Now What are my options?

Sometimes a good cleaning and flush will work to get the assembly to pass the function test.

Sometimes repair parts are needed to get the repair complete and to pass the function test.

Sometimes a complete new assembly is needed to get back to a passing backflow inspection.

When selecting the backflow preventer, make sure you get the right backflow preventer for the application.

Things to consider are:

Lead Free

What is the Hazard Potential

Theft Prevention


Code Requirements

Pressure Loss

Protection against back pressure

Protection against back siphonage

(Composite Plastics, Lead Free Brass, Brass, Stainless Steel)

Below Grade or Above Grade

These are basic concepts that maybe helpful when being notified that your backflow preventer failed.

If you are being told by your backflow inspector that the only option is an expensive repair or replacement, it may make sense to get a second opinion from a reputable backflow prevention service company.


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