Loud water knocking from pressure reducing valve

[Sohcrates]

I have been having an extremely annoying problem for the past several months. Right where the 3/4 copper comes into my house it goes through a Watts pressure reduction valve.

Here is a video

Whenever there is NO water running (all sinks / toilets etc off) the pipes start this rhythmic knocking that resonates throughout the house. It is not a hammering because it only occurs when all the water is off.

As soon as I turn the main water valve off, OR as soon as i open any sink (hot or cold) the knocking stops, and then starts up immediately again when water is turned off.

There is no pattern to this. It occurs variously throughout the day. Sometimes it knocks for an hour and sometimes for less than a minute.

I already replaced the pressure reducing valve with a new one, which one plumber suggested.

Is it possibly the water meter? I assume that would only make noise when water was actually flowing.

It seems sort of like air in the system or something. I did have a new water heater put in last year and they removed my previous expansion tank, telling me it is no longer needed because we have an "open loop" system and therefore the previous owner must have overpaid since it is only needed on "closed" systems.

Thanks

 

[Jadnashua]

A PRV MAKES the system closed. Now, some PRV's can be purchased with a bypass valve, but that sort of negates the whole purpose of having it as it can't bypass back into the system until it gets above the source so it can open the bypass. Plus, public water utilities, to comply with federal guidelines are installing check valves on your supply line as they do upgrades or maintenance, which would also make the system a closed system.

SO, first thing is put an ET back in...then, see what happens.

Pick up a water pressure gauge, preferably one with a second, tattle-tale hand to chart peak pressure, and install it for say 24-hours. My guess is that you'll see the water peaking, especially after you've used hot water enough to cause the WH to turn on.

 

[Sponsor]

 

[Sohcrates]

Thank you. My water heater guy was trying to convince me that I still have an open system and that the ET is no longer required. I sort of believe him because it appears those PRV's with bypasses would still allow backflow, but now I am wondering if like you said there is a check valve at the street causing this.

 

[Sohcrates]

OK. I hooked up a tattle-tale pressure gauge and it was jumping all over the place between 40 and almost 60 psi when the knocking noise was occurring. I just installed a new expansion tank in line with the cold line going into my water heater (where it was installed before).

Interestingly, this HAS significantly cut down on the knocking noise, but not eliminated it. When the knocking continues to occur randomly, the pressure gauge now fluctuates must closer to 45-50 (smaller fluctuation) and the knocking seems less intense. So i think the noise is related to some sort of air / water pressure issue.

Is it possible i have a bad water meter? I was told by the water company that water meter noises would only occur when water is running (a "ticking" sound). But my knocking seems to occur when no water is running?

Thanks for any more assistance!

 

[John Gayewski]

A PRV needs to be sized for minimum and maximum flow rates and periodically cleaned. Also what is your incoming pressure? You need to make sure you're PRV is within its design parameters.

 

[Jeff H Young]

first off even if PRV has a bypass what if you have 160 psi coming in how could your inside reduced pressure "bypass" ?
secondly sounds like a bad PRV

 

[Sohcrates]

It is just odd that the PRV valve was just replaced and is exhibiting the exact same noise as the 10 year old PRV valve.

Though i do agree that perhaps this one is also faulty.

I have never actually tested the main water pressure coming into the house. Is there a way to do that without plumbing in a gauge? I guess i could just bypass the PRV with something temporary and measure it at the sink.

I have always wondered if the PRV is even needed. I think they say only if city is pumping in more than 80 psi.

 

[Reach4]

I have never actually tested the main water pressure coming into the house. Is there a way to do that without plumbing in a gauge? I guess i could just bypass the PRV with something temporary and measure it at the sink.

What is the order of things? Shut off valve, PRV, or is it shutoff valve, tee, PRV?

If the hose spigots tee off before the PRV, measure the pressure at the hose spigot. In any case, you could adjust the PRV to 81 psi and see if the pressure goes that high.

 

[Jadnashua]

Code says that the internal water pressure shall not exceed 80-psi. If yours doesn't, no, you do not need a PRV. If you have a closed system, you DO need an expansion tank. In the city where I live, to pass an inspection, whether it's closed or not, you must have a prv installed as the utility either has, or will be making your system closed, and they don't want issues as they do, so are mandating it now so everything is ready when they complete the upgrades.

A bypass on the PRV can only bypass building pressure back into the system when the building's pressure exceeds the external, source pressure, which means if anything (water heater or just thermal expansion of the incoming water in the heated building) increases the water volume in the house, it will rapidly raise the pressure to the source pressure...sort of defeats the purpose of trying to control it. Common situation...everyone takes their morning shower before school or work, and then leaves...without an expansion tank in a closed system, the WH runs, nobody's home to use any water, and the house sits at that high pressure until someone comes home to use water, or something leaks or breaks to drop it...IMHO, it makes little sense to pay extra for a bypass on a PRV.

Note, to check, you should look for the peak pressure over a typical 24-hour period, as it often can rise at night when there's little use, and they may be trying to pump it up into a water tower to help fulfill the needs for the next day. To do that reliably, you need a gauge with a second, tattle-tale hand.

You might want to check with your neighbors to see if they're seeing similar situations. Your utility could have developed a problem with their nearest pumping station, so a call to the utility might not hurt, either. Near any industrial, large water users? MOst likely is probably a defective PRV.

 

[Jeff H Young]

Take one problem at a time if you need a tank put one in if you don't need one forget the tank. I'm a little thrown off since you already changed PRV but.... have you checked pressure ? does pressure creep up?

 

[Sohcrates]

The house pressure AFTER i installed the new expansion tank is very stable. Rises no more than about 5psi in a 24 hour period.

Before i hooked the tank back up it was jumping easily 10+ psi on and off.

However, when the "knocking" occurs you can see the pressure needle fluctuating up and down.

The order of things is shut off valve directly into PRV and then to rest of house. There is no "T" or anything until well after the PRV.

My next step may be to bump up the pressure through the PRV and see how high it goes or whether that affects anything. I am running about 50psi now.

 

[Reach4]

My next step may be to bump up the pressure through the PRV and see how high it goes or whether that affects anything. I am running about 50psi now.

Good move.

So this knocking occurs often when you are not using water, and have not been using water for the last hour. That would tend to point to sources outside of your house. Are you near a water department building or pumping station? Any industrial user nearby?

 

[John Gayewski]

The house pressure AFTER i installed the new expansion tank is very stable. Rises no more than about 5psi in a 24 hour period.

Before i hooked the tank back up it was jumping easily 10+ psi on and off.

However, when the "knocking" occurs you can see the pressure needle fluctuating up and down.

The order of things is shut off valve directly into PRV and then to rest of house. There is no "T" or anything until well after the PRV.

My next step may be to bump up the pressure through the PRV and see how high it goes or whether that affects anything. I am running about 50psi now.

Are you sure there is no tiny flow somewhere? Like a toilet that fills slowly or something dripping? That will cause a prv to humm because there isn't enough flow. The other possibility is that our just needs cleaned from any kind of debris, including build up.

 

[Sohcrates]

I also am starting to wonder if this relates to something outside the home. I am not close to any sort of station or industrial setup. I will have to ask my neighbors and see if they have a similar issue. Yes, it only seems to occur when there is NOT water being used. But it is certainly possible there is some sort of toilet leak. We had our bathrooms renovated around the same time this noise started as well. Thanks for all the suggestions.

 

[Jeff H Young]

I also am starting to wonder if this relates to something outside the home. I am not close to any sort of station or industrial setup. I will have to ask my neighbors and see if they have a similar issue. Yes, it only seems to occur there is NOT water being used. But it is certainly possible there is some sort of toilet leak. We had our bathrooms renovated around the same time this noise started as well. Thanks for all the suggestions.

I'd try something keep us posted on your results

 

[FullySprinklered]

Seems like I traced a similar problem down to an outside spigot. It had a vacuum breaker on it and had a leaky washer.

 

[Jadnashua]

Try shutting the supply valve to your toilets off and see what happens. Two things to look/listen for:
- does the problem go away
- does the level of water IN the tank drop
It's easy for a small leak into a toilet to be hidden, as the extra water just goes down the drain with little visual indication. Also note where the water level is prior to shutting the water off...it should not be even with the top of the overflow tube...generally, there's about 1/2" or so of clearance between the two.

 

[Sohcrates]

I checked the toilet supply valves and outside hoses, no problems detected.

I also turned the PRV up quite a bit, PSI maxxed out around 55 for the house. Ever since adding the ET and turning up the PRV pressure I have *fingers crossed* not heard the knocking again. Will report back if it continues. Thanks for all the great suggestions.

 

[Reach4]

I checked the toilet supply valves and outside hoses, no problems detected.

I also turned the PRV up quite a bit, PSI maxxed out around 55 for the house. Ever since adding the ET and turning up the PRV pressure I have *fingers crossed* not heard the knocking again. Will report back if it continues. Thanks for all the great suggestions.

It may be that it turns out that you don't need a PRV. You could discuss that with the water department.

 

[Jeff H Young]

Could be that the PRV is not needed you could chase that down, but having a PRV that's unnecessary isn't cause of this noise.
so screwing adjuster all the way noise stopped, suggests to me a bad PRV . I'm still leaning towards a bad reg , don't want you to buy a new one until you are reasonably certain . why not remove it for a test ? some brands with double unions have a PVC jumper nipple that could be purchased .