Failing pressure reducer valve?

Hemlock

I'm hearing occasional sounds from the basement: a sound of rushing air or water that lasts about 2 seconds, followed by a brief "sigh." It happened 3 times last night and once today. It happens when no water is being used in the house. According to google AI, this could be a failing PRV on the main water line or the electric water heater. I did as instructed: turned off the main water supply, turned off the water heater breaker, emptied all water pipes and toilets, and left the faucets open. It's Labor Day so the chances of finding a plumber are slim. I filled several buckets with water before turning the water off.

Questions:

(1) Does this sound like a failing PRV?

(2) Is it more likely to be on the water heater or the main inlet? It sounds more like it's coming from the main inlet, though I haven't been in the basement when it happened. I don't recall the valve on the main inlet EVER being replaced since I've owned this house, which is 35 years (I could be wrong about that—I do know that the water meter on the main line was changed about 30 years ago). The water heater was installed about 10 years ago.

(3) Did I do the right thing by turning off the water etc? Anything else I can do while trying to find a plumber?

Thank you!

EBEBRATT-Ed

The first thing to do would be to get a pressure gauge probably a 0-100 psi gauge you can get one at HD or Lowes or a hardware store. Tell them you want one that fits a male garden hose thread.

The sell them with the fitting on the gauge or you can buy the gauge and the fitting separately.

Put the gauge on ad refill everything. Open a hot water faucet to vent the water heater before turning on the breaker.

If nothing isn't leaking I would not panic. Water pressure on your new gauge of 50psi would be good. See what happens

Jamie Hall

If no water was leaking anywhere… not really a problem. There are only two ways a PRV (pressure reducing valve) can fail: open or closed. If it fails open, all that will happen is that you will have high pressure at your fittings, which might be a surprise. If it fails closed, you'll have low pressure — or none. Either way, not an emergency.

Now if it is a PRV (pressure relief valve) there are again only two ways it can fail — it can fail to open when you need it to, or it can fail to close. If the latter, it will drip or dribble. You can see that.

I'd do what @EBEBRATT-Ed suggested up there. Then the pressure test will tell you if it is the reducing valve — and wandering around the basement you can find the relief valve and see if it is dripping. Then find a good plumber and arrange for them to check and fix the problem.

109A_5

The whole " google AI " thing sounds like a bit much, especially if there is no evidence of any leaks. It sounds like instructions as if the heat failed and the pipes are going to freeze scenario.

Anyway I'd put everything back to normal and try to identify where the sound is coming from. Paying a Plumber to find a noise that only happens 4 times a day may be disappointing.

From here it sounds like it may be a toilet flapper valve that has a slow leak and the fill valve is just topping off the toilet tank as needed when needed.

HVACNUT

Leaking toilet flapper?

EBEBRATT-Ed

I didn't think of a toilet flapper that is a good idea

Hemlock

A plumber came today and checked the water pressure etc. He didn't find any problems. He gave me a pressure gauge and asked me to check the water pressure a few times a day. We turned the water back on.

hot_rod

A gauge like this on a hose bib will show if you are getting pressure flucuations.

When the water heater warms, pressure increases ins the system. Some PRVs allow that pressure to go backwards through the PRV, that could be the noise you hear. Generally at days end when no water is being used, the water heater catching up.

Is there a back flow device at the PRV? If so, have it tested and you need a thermal expansion tank.

mattmia2

you also may hear water flowing as the pressure in the main changes. when i had a water heater with mechanical heat traps i would hear them clicking whenever something with a solenoid valve closed or when the main pressure changed. The part of the system I am on is pumped out of a tank so the pressure varies as the pumps switch on and off or change speed.

hot_rod

it kinda depends on the specific prv

Caleffi PRVs are all pressure balanced

So if you set it at 45 psi while incoming main is 80 psi, if the main rises to 100 psi the regulated pressure does not change

Other brands, non pressure balanced, the set pressure will vary some with main incoming pressure changes

Hemlock

I checked the pressure at the hose spigot two days in a row and it was 55. The noise hasn't happened again. Hopefully it was just a fluke. I heard it only in the evening so I noted this comment by Hot Rod: "When the water heater warms, pressure increases in the system. Some PRVs allow that pressure to go backwards through the PRV, that could be the noise you hear. Generally at days end when no water is being used, the water heater catching up." Is that normal and not a concern?

Jamie Hall

If you have a pressure reducing valve or any other valve which functions as check valve between your water source and you how water heater, you must have an expansion tank on the hot water. It doesn't have to be that large, but it has to be there. Sounds as though your don't…