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Chicken or egg question

Chicken or egg question

Chicken or egg question

When installing a backflow preventer and PRV in series, which would you install first and why?

I choose the PRV first, then BFP arrangement, since I always assume the more moderate the pressure imposed on a system component (e.g., the BFP), the better.

Does it matter?

RE: Chicken or egg question

If the installation is a water service into a building, typically the only equipment that are allowed upstream of a backflow preventer is a strainer or a check valve. This is typically an AHJ requirement.

If the installation is to protect the building water from a non potable use, i.e. cooling tower make up, there is no issue.

RE: Chicken or egg question

I've found that it's a water provider (water works) preference if any rather than a code issue. Most require the BFP at the property line just past the meter, so that settles it. But in areas where no preference is specified and we have a PRV-BFP or BFP-PRV arrangement, the PRV first makes more sense to me.

We work in a lot of remote areas where the AHJs acquiesce to whatever we draw and stamp.

RE: Chicken or egg question

I can't really see any one being better than the other. Backflow could only occur due to low pressure in the incoming supply, in that case the Pressure regulating valve (I initially read it as Pressure relief Valve...) will probably be open trying to feed the downstream supply pressure and essentially become a piece of pipe and has no effect on flow.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Chicken or egg question

I have never proposed doing it, but it can be done if the upstream pressure is above the maximum allowable for the backflow preventer. Most of the ones I use have a maximum pressure of 175 psig. If you have that much pressure, you would be in the minority.

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