Water surges after installing pressure reducing valve.

[coffeeandplumbing]

Howdy folks, first time poster here. I am a residential service and repair plumber in Bay Area, California. I've been at it for over 9-1/2 years now and recently started my own company!
I'm having issues troubleshooting this problem. I think it is related to the installation of a pressure reducing valve. I installed a pressure reducing valve on my house (I live in an in-law unit) after my landladies complained of an excessive water bill. Our water usage dropped after installing the PRV (and I explained the important of a PRV to help reduce wear and tear on plumbing fittings, and reducing the chance of bursting/failure) but now I notice when turning on the faucet, sometimes there's a "surge" of water, maybe 3 seconds or so, and then the pressure drops to the operating pressure of the PRV. So somehow the pressure is building up in the supply line.
My guess is that since the PRV has a built-in backflow preventer, it is not allowing pressure to escape. Our water heater does not have an expansion tank, which would accommodate the pressure build up. This is only my guess; can anyone confirm?
I was just ignoring the problem because it really was not a big deal, but a client of mine recently reported the same issue after installing a pressure reducing valve. They do not have an expansion tank on their water heater, either. They may have me replace their water heater and I will be installing an expansion tank.

 

[spcwaters]

I imagine your on city water? They usually have a check valve in the meter box around here. If you install an expansion tank. It will allow for thermal expansion. As it is now, when thermal expansion occurs, there's no where for the expanding water to go. Thus increasing pressure.

 

[havasu]

Just to confirm, you have the direction of the arrow on the PRV pointed the correct way?

 

[frodo]

has the double ck backflow preventer been tested/certified as per local codes?

when it was installed was pipe dope used? using pipe dope is a no no, teflon tape only

 

[coffeeandplumbing]

I imagine your on city water? They usually have a check valve in the meter box around here. If you install an expansion tank. It will allow for thermal expansion. As it is now, when thermal expansion occurs, there's no where for the expanding water to go. Thus increasing pressure.

Yes - on city water.

Just to confirm, you have the direction of the arrow on the PRV pointed the correct way?

Yes, the PRV is installed in the correct direction

has the double ck backflow preventer been tested/certified as per local codes?

when it was installed was pipe dope used? using pipe dope is a no no, teflon tape only

There's no double check backflow preventer on the house. Just the Pressure Reducing Valve (Watts) which I believe have a backflow preventer built in.

I used pipe dope and then teflon over the pipe dope on the threads. I used to only do one or the other but within the last year switched to doing both with no problems. I don't think the pipe dope would cause any problems, what are your experiences with pipe dope causing issues?

Thanks for the responses everyone.

 

[frodo]

about a $360.00 dollar learning curve, had 3 of the installed in the ceilng over the coke/ice tea station of a cafteria
that would not shut off, the certifier had to take them apart and clean them to certifier. @ $120.00 each
he told me, never, never ever, never ever ever dont F____ use pipe dope, only tape

it gets inside the valve an gums the springs/diaphram up. has to be takin apart and cleaned because they leak
the $360.00 made a believer out of me

 

[spcwaters]

Yes - on city water.







Yes, the PRV is installed in the correct direction







There's no double check backflow preventer on the house. Just the Pressure Reducing Valve (Watts) which I believe have a backflow preventer built in.



I used pipe dope and then teflon over the pipe dope on the threads. I used to only do one or the other but within the last year switched to doing both with no problems. I don't think the pipe dope would cause any problems, what are your experiences with pipe dope causing issues?



Thanks for the responses everyone.

If you don't have a thermal expansion tank, I'd throw one on there. It's the first thing I'd do.
I mean if you think about it, in a closed system you have 0 room for expansion, a basic understanding of water, will tell you when it gets hot, it expands. Pressure is the byproduct.

 

[ExtraMilePlumbing]

And inflate the expansion tank to match the pressure at the house

 

[Mr_David]

Sometimes even a new PRV can leak through.
Maybe a little debris got on the seal.
Put a gauge on the system and let it set for a few minutes or longer if needed.
Turn the water heater off so you won't get any thermal expansion.
Maybe run some hot water out of the tank before you test for thermal expansion.

Then after you are satisfied the surge in pressure is not coming through the prv fire up the water heater and see if the pressure goes up.

When I get high pressure readings on a unit, I bleed off some pressure and if the gauge starts to climb slowly up, I go find the wtr htr and make sure it's not cooking. If it's not cooking then it must be the PRV leaking by.

 

[KnarlyCarl]

You mentioned Watts, now I'm curious to know the model no.?
It may be referred to as reduced principle backflow preventer

 

[ExtraMilePlumbing]

about a $360.00 dollar learning curve, had 3 of the installed in the ceilng over the coke/ice tea station of a cafteria
that would not shut off, the certifier had to take them apart and clean them to certifier. @ $120.00 each
he told me, never, never ever, never ever ever dont F____ use pipe dope, only tape

it gets inside the valve an gums the springs/diaphram up. has to be takin apart and cleaned because they leak
the $360.00 made a believer out of me

Is that a regular prv valve you are talking about or a double check valve back follow preventer?

 

[KnarlyCarl]

Double check and backflow preventer are two different things

 

[coffeeandplumbing]

You mentioned Watts, now I'm curious to know the model no.?
It may be referred to as reduced principle backflow preventer

It was one of these:

http://www.zoro.com/watts-water-pressure-reducing-valve-85-psi-34-lf25aub-hp-z3/i/G5365437/?gclid=CjwKEAiA58a1BRDw6Jan_PLapw8SJABJz-ZWhrfHWx5AkG9BJsm4scZpfAZgRrSpXP1IUA8q4Q6TrRoCLanw_wcB&gclsrc=aw.ds

Except it adjusts pressure to between 50 PSI and 80 PSI.

 

[KnarlyCarl]

Had you gotten any further with this? Did you put gauge on or put an expansion tank on water heater? Did you find out for 100% sure if there is a check in the prv?

 

[Mr_David]

Double check and backflow preventer are two different things

How so? a double check is a backflow preventer but a backflow is not necessarily a double check.

 

[Mr_David]

Is that a regular prv valve you are talking about or a double check valve back follow preventer?

Sometime a reduced pressure back flow preventer is called a double check valve but they are not the same.

Here reduce pressure valves are used.
They have a dump valve between the checks.
Double check are not used any longer.

 

[ExtraMilePlumbing]

Cool thanks for that mr David