PRV vibration

[Reach4]

Could I use up the hot water and then do the test instead of letting the water cool down?

Not necessary. Once the WH is off, the water will not expand.

The thought about keeping the WH off for a longer period had to do with what if there is no howl. Is that lack of howl just because it is intermittent, or will there never be a howl with the WH is not expanding water.

It's my guess that the howl will still happen with the WH off. My guesses are often wrong. My thinking is that the howl occurs while a little water is being used, so no thermal expansion overpressure should exist.

 

[Mliu]

Could I use up the hot water and then do the test instead of letting the water cool down?

Absolutely! The problem is not the water that's already hot; the problem is caused by the cold water being heated.

 

[Sponsor]

 

[Mliu]

It's my guess that the howl will still happen with the WH off. My guesses are often wrong. My thinking is that the howl occurs while a little water is being used, so no thermal expansion overpressure should exist.

Even when water is being used only intermittently, if cold water is being heated, the pressure will rise whenever all the faucets are closed. They don't have to be closed for hours for high pressures to build. The pressure doesn't have to reach the point where the Temp & Pressure Relief valve pops. Any pressure downstream of the PRV that's higher than what the PRV is set to can cause this kind of vibration.

 

[kami25]

Still humming.

 

[Mliu]

Still humming.

How long has the heater been off?

Btw, is your heater gas or electric? How did you turn it off?

 

[kami25]

Left it off for 2 hours. Turned the gas off. I used lots of the water doing wash, etc. I think I used enough and it cooled enough for it not to expand back into the pipes.

 

[Mliu]

Ok, so the problem appears to be solely with the PRV. But before we condemn the Watts, consider that the LFN45B-M1 PRV has been in service since at least 2016. Its non-lead-free predecessor (since discontinued) was in service since at least 2012. In the past 8 years, Watts has probably sold tens of thousands of these devices. If they had a design flaw, it either would have been corrected long ago, or there probably would have been a class-action lawsuit by now.

You said that when you first installed the PRV, there were no problems; the vibrations started after several days. I believe that the high pressures caused by the lack of an expansion tank damaged the PRV internals. After that, the vibrations started.

Btw, how old is your water heater? When you have the plumber come out, you should have him inspect your water heater's TPR valve. It may not be operating correctly.

 

[kami25]

I thought too about the back pressure damaging the PRV . I called Watts and asked the tech. twice about having no expansion tank and damage and he said no it will not cause damage to the prv.

 

[Reach4]

I thought too about the back pressure damaging the PRV . I called Watts and asked the tech. twice about having no expansion tank and damage and he said no it will not cause damage to the prv.

Did you ask what you should do now, given your situation?

 

[kami25]

Called Watts and they said to upgrade to the 55. The plumber had already suggested that and today in put in a Watts but different model. He said the one I had just can’t handle the street water pressure. No humming /vibrating. When I was on the Home Depot website there were several complaints about the model I first tried. It just doesn’t seem to be able to handle high pressure from the street.