PRV Droop?

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ErikS2015

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We had a PRV (Wilkins NR3XL) installed a while back to help with high supply pressure (90 to 100 psi at night). It always seemed like the flow from some of the faucets would drop off rather dramatically shortly after the water was turned on. Last weekend I finally got around to putting a gauge on an outside faucet that is about 5 feet of pipe beyond the PRV. The gauge showed around 60 psi as the setpoint. But, as soon as I turned on a sink faucet, it dropped down to 40 to 45 psi. Is this typical for a PRV? The flow curves for this model on the Wilkins website would suggest it should be more like 5 psi (??).

Thanks,
Erik
 

Reach4

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Turn on a cold faucet to a dribble. What pressure do you get then?. Then turn off that faucet. What happens to the pressure? Falls how quickly? Rises how quickly?

Your symptom could be one of a few things. One would be that the PRV is actually set to 45 or 50, and it leaks a bit. The pressure tank should be able to compensate for a tiny bit of leaking.

A couple of the possible problems could involve your pressure tank having a problem. Turn off the water coming in. Open a cold faucet. The pressure tank should be empty. Knock on it to find out. Measure the precharge air pressure. Try setting the precharge on your pressure tank to 50 if it is currently below 50. If water comes out of the schrader (tire) valve, replace the tank. If it will not maintain the precharge, replace the tank. If the pressure tank is OK, fix or replace the PRV.
 

ErikS2015

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Turn on a cold faucet to a dribble. What pressure do you get then?. Then turn off that faucet. What happens to the pressure? Falls how quickly? Rises how quickly?

Your symptom could be one of a few things. One would be that the PRV is actually set to 45 or 50, and it leaks a bit. The pressure tank should be able to compensate for a tiny bit of leaking.

A couple of the possible problems could involve your pressure tank having a problem. Turn off the water coming in. Open a cold faucet. The pressure tank should be empty. Knock on it to find out. Measure the precharge air pressure. Try setting the precharge on your pressure tank to 50 if it is currently below 50. If water comes out of the schrader (tire) valve, replace the tank. If it will not maintain the precharge, replace the tank. If the pressure tank is OK, fix or replace the PRV.
 

ErikS2015

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Good call on the expansion tank failing. It had. Bladder was full of water. It had lasted about 5 years.

So... new expansion tank installed (increased it from 2.5 gallon to 5 gallon as well, since 2.5 gallons was listed as marginal for a 50 gallon water heater). Set precharge pressure to 50 psi or so. Water pressure generally seems to stabilize at 55 to 60 psi. The droop problem is still there. With the kitchen sink on low, it drops about 15 psi over a period of a few minutes. It recovers in a minute or so. A tub filling drops it about 30 psi.

So... sounds like a new PRV or a rebuild is next. Unfortunately, the plumber who installed it only put a union on one side. So, I have to decide on try to remove the guts in place, or take it out, chop a bigger hole in the wall, and add a second union.
 
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