Pressure Regulator Valve broken?

20 year old house. I am the 2nd owner. Bought the house in May 2008.

There is a Cash-Acme EB-86 PRV just behind a gate-valve house shutoff-valve. Both PRV and gate-valve look original.

I used a $10 Orbit water pressure gauge from Home Depot and measured pressure on the garden hose bib, which I believe is regulated since the pipe came out of the house and is apparently controlled by the house gate-valve.

Ok here are the observation:

1) Static water pressure varies from 90 - 110 psi, depending on the time of the day. I adjusted the screw on the PRV but it did not make any difference.

2) When a faucet is opened, water rush out, then after five to six seconds, water flow is noticeably reduced, but still at a usable rate. When PRV is adjusted counter-clockwise, water still rush out, but the flow rate after five seconds is reduced, compared with before adjustment.

3) I am not able to find any water expansion tank in the house. I have not measured the hot water pressure yet as I don't know where to attach the gauge. Hot water from faucet behaves pretty much the same as cold water: water rush out then flow slows after five seconds.

4) After a faucet is turned off, I can still hear water flowing in the pipe for four or five seconds before it stops. The sound is especially noticeable in the garage where the PRV and house shutoff valve are located.

From what I read here and elsewhere, it seems that I should keep the static water pressure to at or slightly below 80 psi. So here are the questions:

1) Is my PRV broken?

2) Do I need a water expansion tank?

3) Where was the water flowing to after I turned off faucet? (This question puzzles me a great deal.)

Thank you so much.

newowner123

The PRV is bad. It can NOT be ADJUSTED to deliver a pressure higher that 80, so when you see a higher pressure, it is because the diaphragm is leaking by. THe pressure drops when you run a tap, because the PRV is trying to regulate, but in the absence of flow, it just bleeds by unitl house pressuer equals street pressure.

An expansion tank is not related. It prevents TEMPORARY pressuere build up when the water heater is heating a new load of cold water. It cannot deal with a permanent high pressure.

Just get a new PRV. Then check the pressure build up during heating cycle, to see if you need an expansion tank. ( All WH manufacturers today, and some building codes, require it )

The PRV needs to be replaced...in my area they also require a Watts #7 double check valve or similar.

With the PRV and or check valve you need an expansion tank also. The pressure of the tank should also be set at or 1-2 #s lower than the house pressure.

Thank you jimbo and Cass. I replaced the PRV and static pressure now is 65 psi. I will test pressure again after heating cycle.

Ok so the good news is static water pressure is stable at 55 psi. Bad news is after WH shuts off, thermal expansion pushes that up to 100 psi. Flushing a toilet drops that to 55 psi.

So if I take a shower and leave house for work, the pipes are going to endure 100 psi for the whole day. Would all you experts agree a thermal expansion tank is needed?

I would put on a tank...

PRV and an expansion tank almost always need to be installed together.