Loud water knocking from pressure reducing valve

[Jadnashua]

Does the house pressure change when you change the PRV adjustments? If it say rose from 40psi to 55 as you adjusted, but didn't go further, it may be okay...but if it was at 55 when you started, and didn't change, then either the supply is at 55, or the prv is bad. Sometimes, it nice to have a pressure gauge, or a port where you can check it, both before and after the PRV.

 

[Jeff H Young]

Does the house pressure change when you change the PRV adjustments? If it say rose from 40psi to 55 as you adjusted, but didn't go further, it may be okay...but if it was at 55 when you started, and didn't change, then either the supply is at 55, or the PRV is bad. Sometimes, it nice to have a pressure gauge, or a port where you can check it, both before and after the PRV.

Definitely good to have a spot that's not on the regulator to check, he might have 55 psi coming in or it could be more impossible to know the pressure based on provided info.

 

[Sponsor]

 

[Sohcrates]

So I still get the occasional knocking. I just tried adjusting the PRV down (instead of up) and it doesn't really change anything. Still hovering around 50-55psi. That alone seems to tell me that it may indeed be a bad PRV at this point.

Does anyone know if it matters what "type" of PRV I replace it with? I currently have a Watts setup but there seem to be many alternatives out there.

 

[Jeff H Young]

I dont think it matters as long as it can supply needed volume. I use watts brand and zurn/wilkins. i guess you never determined the water pressure or if you need a regulator?

 

[Bannerman]

I just tried adjusting the PRV down (instead of up) and it doesn't really change anything.

When reducing the pressure setting on a PRV, a downstream faucet will need to be open slightly so as to relieve the initial higher pressure after the PRV. When there is no water being drained downstream, the pressure after the PRV will not usually change regardless of how much the pressure is being lowered.

 

[Bannerman]

To assist to determine the source of the sound, use a long screwdriver equipped with a hard handle (not rubber covered). Use the screwdriver as a makeshift stethoscope by holding the tip firmly against the suspected source of the sound (PRV, water meter, water heater TPRV or other device). Place your ear against the handle to attempt to determine where the sound will be sharpest and most intense.

If the water pressure from the city is less than 80 psi, a PRV should not be needed, but perhaps your home is located nearby to a pumping station which may cause the mains pressure in your area to exceed 80 psi whenever that pump is operating.

 

[Jeff H Young]

Tried telling him to check pressure if you don't know what's incoming you can't know if regulator is needed or doing anything

 

[Sohcrates]

I am planning to replace the PRV and before I do that I have an adapter to check the water pressure from the city I will install. Planning to do this before the holidays. Will also check with the "stethoscope" to verify where sound is coming from.

 

[Reach4]

I am planning to replace the PRV and before I do that I have an adapter to check the water pressure from the city I will install. Planning to do this before the holidays.

I would ask the water department if they expect that you need a PRV. Also consider talking to a neighbor or two if they have any knowledge of the local conditions.

But yes, a way to measure pressure before the PRV is good. I would not like to have a PRV if the pressure from the street is only 55 or 60.

 

[Jeff H Young]

We have no idea what the max pressure to the house is only that where and when he checks it, it as least 55 but whether it rises in off times low demand who knows ? We can only repeat these obvious things to the OP and hope he gets it.

 

[Bannerman]

The 200 psi gauge example linked to below, includes a 'maximum pressure' pointer which will indicate the maximum pressure sustained since the pointer was last reset manually. The garden hose adaptor fitting maybe removed so as to thread the guage to an alternate fitting before the PRV.

https://www.amazon.com/Watts-0950200-Water-Pressure-Gauge/dp/B000YMU8JC/ref=sr_1_6?crid=140LRMJ21UPVI&keywords=water+pressure+gauge+with+max+pointer&qid=1638376435&sprefix=Water+pressure+gauge+with+,aps,341&sr=8-6&th=1

 

[Sohcrates]

OK, good news (i think)

I replaced the entire PRV and things seem better.

When i replaced i measured the city pressure and it was around 60 psi.

Of course, i then questioned WHY I have a PRV to begin with, but it seems many of my neighbors do as well.

I have not heard any knocking since adding the expansion tank and now replacing the PRV.

Thanks for all the help.

 

[Reach4]

Of course, i then questioned WHY I have a PRV to begin with, but it seems many of my neighbors do as well.

Good question. The neighbors' houses may have been built at about the same time and maybe by the same builder. It was probably not known what the incoming water pressure was going to be, so they put in PRVs out of caution.

I would ask the water department what the max pressure is that they intend to supply in the foreseeable future.

 

[Jeff H Young]

I can't tell you why its there (PRV) can only tell you reasons they are normally installed. Also can't tell you why lots of your neighbors have or don't have one.
If I'm familiar with an area where pressure is consistently low and building department and water department says I don't need one I don't install it, If one or both tell me I need one I install the PRV then I will. If I check and determine the pressure is high I install one.
Don't care about what the neighbors did 2 years ago or 20 years ago. Also sometimes I inquire about future changes to infrastructure but generally worry about current conditions and requirements of AHJ.

 

[Jadnashua]

Water pressure can vary, and often rises overnight. As a neighborhood is built out, it may initially be high, but as more and more houses are built, the pressure can drop. So, what was true when the house was built, may no longer be true. The utility may decide it needs a different pump to handle additional customers, and that can raise your pressure sometimes, too.

At night, when few people are using water, the pressure can rise, especially if there's a water tower they're trying to refill. This is why a single, momentary sample of water pressure won't tell you whether you really need a PRV or not. You need to use a gauge with a second, peak-reading hand and leave it attached at least for 24-hours to see what's going on.

 

[Jeff H Young]

Water pressure can vary, and often rises overnight. As a neighborhood is built out, it may initially be high, but as more and more houses are built, the pressure can drop. So, what was true when the house was built, may no longer be true. The utility may decide it needs a different pump to handle additional customers, and that can raise your pressure sometimes, too.

At night, when few people are using water, the pressure can rise, especially if there's a water tower they're trying to refill. This is why a single, momentary sample of water pressure won't tell you whether you really need a PRV or not. You need to use a gauge with a second, peak-reading hand and leave it attached at least for 24-hours to see what's going on.

Sochrates is dealing with loud noises has a new PRV and expansion tank and noise stopped. I've thought it was a bad regulator all along but it stopped , no idea as to whether he needs a regulator but I'm pretty sure his old one was bad.
I'm not guessing he needs a regulator or not and he doesn't seem interested in, in finding out, I would do more testing as Jadnashua mentioned and even more extensive and check with water provider as to whether they recommend a PRV and if so why they believe its needed.