Water pressure regulator

Hi everyone,
I'm new to this forum, but I was hoping to get some advice before I call a professional. We have a Watts N35B pressure regulator with a range of 25-75 psi, set to a standard of 50.

I measured the pressure (with a watts gauge) at the front hose and it was 60 psi (give or take a few psi). The red needle, that shows spikes, shot up to 100 psi. Just to make sure it wasn't thermal expansion (because we don't have an expansion tank), I checked the pressure again after the dishwasher was running and the water heater was going. The static pressure was 67 and the spike went to 80.

Is our pressure regulator malfunctioning? We tried to reduce the pressure by adjusting the screw, it wouldn't go below 57 psi. At least it seems to control the pressure to a 57-67 range, but the spike seems a little high. The water company said the incoming water pressure is usually around 80 psi.

I could call a professional to get an estimate on replacing the pressure regulator for the same model if that is what is broken. Might also solve some water hammer issues (although that problem seems more related to abrupt slamming of the faucets and my family refuses to listen to me!). Thanks.

Your PRV may need cleaning and adjusting, or perhaps be replaced, but you really should have an expansion tank. I am surprised your T/P valve does not trip when the water heater is on.

The PRV has a thermal expansion bypass, which explains why the static pressure stayed around 60 when the water heater was running. Still doesn't explain the spikes past 75, which is the max of the PRV. I guess I'll call around for estimates at this point.

You need to check and see what the pressure does without the water heater running.

I See Same Thing

I have observed similar results at my house (15 years old) with same Watts PRV. I believe the PRV to be failing and not closing all the way when water is off. County water dept. says pressure at my nearby fire hydrant is 78 PSI and when all faucets are off I see 78 PSI. When any one faucet is open a little bit and a stream of water is runnning, I see 60 PSI and if I adjust PRV this value changes. BUT if I close faucet, it drifts up to 78 PSI no matter how PRV is adjusted.

Here is my theory, if street pressure is 78 PSI, the only way a PRV could keep house at 60 PSI is if it completely closes. Then when faucet opens, pressure in house drops, PRV partially opens and regulates pressure. My guess is that after 15 years the washer/seat/seal (or whatever it is) is worn/dirty and is not longer completely sealing off the house from the street, hence the house pressure drifts up toward street pressure when all faucets turned off.

If I have this correct, then the PRV sees a total # of on and off cycles equivalent to the sum of all the on/off cycles of all the faucets, washers, icemakers, etc. in the whole house. Not surprising its lost its seal after 15 years........

wraujr said:

I have observed similar results at my house (15 years old) with same Watts PRV. I believe the PRV to be failing and not closing all the way when water is off. County water dept. says pressure at my nearby fire hydrant is 78 PSI and when all faucets are off I see 78 PSI. When any one faucet is open a little bit and a stream of water is runnning, I see 60 PSI and if I adjust PRV this value changes. BUT if I close faucet, it drifts up to 78 PSI no matter how PRV is adjusted.

Here is my theory, if street pressure is 78 PSI, the only way a PRV could keep house at 60 PSI is if it completely closes. Then when faucet opens, pressure in house drops, PRV partially opens and regulates pressure. My guess is that after 15 years the washer/seat/seal (or whatever it is) is worn/dirty and is not longer completely sealing off the house from the street, hence the house pressure drifts up toward street pressure when all faucets turned off.

If I have this correct, then the PRV sees a total # of on and off cycles equivalent to the sum of all the on/off cycles of all the faucets, washers, icemakers, etc. in the whole house. Not surprising its lost its seal after 15 years........

Click to expand...

You are correct it has failed.

natalie1999 said:

The PRV has a thermal expansion bypass, which explains why the static pressure stayed around 60 when the water heater was running. Still doesn't explain the spikes past 75, which is the max of the PRV. I guess I'll call around for estimates at this point.

Click to expand...

You would need to know the street pressure as the house side pressure would need to exceed the street pressure for the PRV by pass to work...

spikes

We need to know if the "spikes" occur gradually, which would indicate that the valve is failing. Or if they come quickly, but intermittently, which would be the result of closing faucets rapidly. In any case, with an 80 psi main system, you really don't need the PRV in the first place as long as it is consistant.

The street pressure, or the main water pressure from the street, is 80 psi. Whether that is consistent or not is not something the water company seems to guarantee. I'm pretty sure the thermal bypass works because I checked the pressure when the dishwasher (thus the water heater) was running (67 static, 80 spike). I also checked after it was done (60 static, 80 spike).

The 100 psi spike occurred when nothing was running and in the morning.

At this point, it's turning into a puzzle so I set up an appointment with a professional plumber to see if the water pressure regulator is working properly or not.

What got you curious about the water pressure in your house¿ The water hammer¿

Yeah, there's some noise in the upstairs bathroom. It's not that bad, apparently only I can hear it (I'm sensitive). Definitely helps if people didn't close the faucets so fast. Not enough room under the sink to put water hammer arrestors.

Also slight tapping noise in the downstairs bathroom after using the toilet or sink, not enough room there either to install WHAs. In any case, once again, no one else really notices.

So I just wanted to check the pressure to make sure that wasn't causing any problems. Our pipes are all cpvc, except for the main water line, which is I think copper. House is 8 years, going on 9.