backflow preventers

tommy

I've gone through 2 watts backflow preventers and both
vent constantly. I broke down and installed a 25-75 prv
in the domestic water line prior to the backflow device
at the hot water boiler. I reduced the pressure and I
still have the same condition.Can anyone provide some
insight as to what the problem might be.

Thanks, tommy

Unknown

When you install a p.r.v. you "close" the water system, meaning there is no room for expansion. You may need to install a domestic expansion tank(thermxtrol). This should help.

Heatermon

What Model backflow are you using.

And what is it being used for? Also,by "venting" do you mean the relief valve is discharging?

Heatermon

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Andy N.

backflow preventers

what kind of backflow preventer are you using? If you are using an rpz you might want to check for pressure fluctuations on the inlet side. this will cause intermittent discharges. this problem can be solved by installing a check valve upstream of the rpz. the other problem you may be seeing is poor water quality entering the backflow device. you should have a strainer installed in front of it. Then again are you sure it is a watts backflow preventer and not a relief valve?


Hope this helps

Andy

Dave Yates (PAH)

You need

a soft seated check valve ahead of the RPZ to stabilize and maintain the elevated pressure. Otherwise, you'll continue to see discharges when the inlet pressures fluctuate and drop more than 2 psi below the downstream static pressure. An upstream PRV can aggravate, rather than help, this condition.

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