Potential water hammer issue?

[kitsune]

Sorry for the long post but I think all this info could be helpful??
It seems like this may not be a water hammer issue since water hammer is only when you close the valve thats when you hear the water hammer, but in my case I only hear the banging when opening the cold water.

Been living at this home when it was first built in 2002 (located Weston, WI) and have never experienced this issue before. Also all water lines are copper.

- January 2023 my water heater t&p valve was leaking so that valve was replaced.
- February 2023 my old man snapped the toilet flush valve so had to replace that and buy a new gasket where the tank seats to the bowl.
- Around late February or late March 2023 we notice a light 1 second bang after we'd flush the upstairs toilet. We thought nothing of it and let it go by then eventually the banging got louder lasting 1-3 seconds. We looked at the water pressure gauge on the main water line and noticed that it would slowly creep up past 60psi going into 70-90 psi.
- We tried the method of shutting off the main water line then opening all faucets to drain completely and slowly opening the main water line but the banging still remained.
- We've tried replacing the toilet fill valve and the noise still remained.
- We've tried turn the water shut off valve to the toilet to a 1/4, 1/2, 3/4 turn and the banging still remained (its a quarter turn water shut off valve).
- Then we noticed that same banging also started to occur when we use the cold water in the kitchen, note that only when the cold water first turns on the banging noise is heard for 1-3 seconds but when we turn it off rapidly or slowly the banging is never there.
- Then the noise also was heard when we turn on the garden hose bib as well.

We'd thought that it might be be the same with the hot water too so we tested all faucets on the hot water side opening it rapidly, slowly, closing it rapidly and slowly but the water hammer banging noise was never heard so this narrows it down to the issue is only on the cold water side.

- Gave up and called a plumber and they came and said our PRV is most likely bad so they replaced the PRV on the main water line then the banging disappeared for about 3 weeks. After those 3 weeks the noise came back again so we called that plumber back again they took a look at the PRV, took out the screen and everything looked new and no sediments were present at all so they replaced that PRV with another new PRV and the the noise was still present after the install.
- After that they replaced the toilet fill valve even though we just replaced it with a new one and the noise was still there so they just left our existing fill valve there.
- Then they added water hammer arrestors, 2 on the cold water line in the basement and 1 right before the toilet fill valve and the noise never went away either.
- After all that it seemed like they were stumped so they said they cant do much besides try to add a thermal expansion tank to the water heater or take down the walls to see if the water lines are secured or not. We eventually said no to both as it would of been costly.
- So we called 2 more different plumbers and they went through exactly what the previous plumber did and they said "yeah everything has been added on and if we'd like to try the thermal expansion tank that would be the next best least invasive route or we could open up the walls to see if the water lines are secured or not"
- After that I turned the PRV water pressure down to 40psi and noticed that it would actually hold the pressure there most of the time and if it were to rise it'd probably go up 20-30 psi and we noticed that the banging was not as loud anymore for about the next few month.
- Then probably around November 2023 I turned the PRV pressure back up to 60 psi and it was holding it there for a while and the banging noise miraculously disappeared until now
- Yesterday 9/9/2024 we replaced the water heater with the same Richmond Essential 40 gallon natural gas water heater since our water heater stopped producing hot water consistently and was about 9 years old. After replacing it, we noticed that today that exact same water hammer banging noise is back at the same toilet and other faucets that uses cold water.
- Today 9/10/2024 I've tried swapping the toilet fill valve with a new one and still the same issue
- Also have tried messing around with the water shut off valve to the toilet again and noticed that at 1/4 of a turn to opening it up the noise is somewhat gone?? Sometimes it is there but not as often? And if I open it fully and try flushing the banging noise is back.
- But also am noticing that same banging noise when opening up the hose bib too (even at any setting of toilet water shut off valve)
- Currently it is set to 60 psi and would creep up to 70-75 psi sometimes and even at 60 psi the banging would happen only when turning on/opening a cold water valve such as the outdoor hose bib or flushing the toilet.
- For some unknown reason at other water faucets and toilets in the house it does not produce that banging noise
I guess the next stuff to replace would to the water shut off valve to the toilet but I'm not sure if this is the culprit??
- Also the banging noise does not come on all the time too, its kind of like every other time or almost everytime when in use

Also would I need a thermal expansion tank because when the home was first built it never had one and I've asked the neighbors around me if they have thermal expansion tank and they all do not have one either. Or how to deduce if I really need a thermal expansion tank?

Given all the things I've tried what else could I try if the new water shut off valve does not fix the banging?

TLDR; Might not be water hammer but banging noise appeared then disappeared and now is back again only when opening cold water faucet (outdoor hose bib, upstairs toilet flushing). Turning it off does not produce the banging noise. Note that issue is not present with the hot water. The noise also does not constantly come on all the time too.

 

[kitsune]

Well did some more digging around in my basement and see that its copper to pex and all lines are secured pretty well and still cant figure out where the banging is coming from. Tried lowering the water pressure to 30 psi and it seems to be stay around 30-40psi and sometimes it does bang when turning on the water but not as often and intense, but now its almost at any water faucet/fixture. First thing I'll do for now is install a thermal expansion tank after some research I'd say it is needed and to return the pressure back to 50 or 60psi and to replace the toilet shut off valve. I'll report back on here if any of this helps or not

 

[Sponsor]

 

[Bannerman]

It seems like this may not be a water hammer issue since water hammer is only when you close the valve thats when you hear the water hammer, but in my case I only hear the banging when opening the cold water.

Water hammer will occur most frequently when a valve is closed rapidly, but can also occur under certain circumstances when opening a valve.

When cold water is heated, as occurs within a water heater, the water will expand. As water cannot be compressed, even a small amount of expansion when there is no provision to absorb that expansion, will cause the plumbing system static pressure to rise rapidly and significantly.

The PRV on the municipal supply line will act as a one-way valve so the expansion occurring in the WH, cannot push backward through the PRV to the municipal water main, resulting in your home's plumbing pressure rising significantly above the PRV pressure setting.

Hot water usage patterns will influence the amount of pressure rise as will the WH temperature setting. A long shower will result in a greater amount of cold water to be heated, compared to a shorter shower, and hot water use directly before bed, will typically result in elevated pressure throughout the remainder of the night, until any water is again used.

While opening any faucet will cause the additional pressure to be rapidly relieved, that sudden drop in pressure, particularly when the pressure is greatest, maybe causing the PRV to shudder, so it maybe vibrating rapidly, creating shock waves downstream throughout the home's entire plumbing system.

When there is a check valve or PRV located between a WH and a municipal water main, a thermal expansion tank is an absolute necessity. The expansion tank will absorb water expansion, thereby minimizing any resulting pressure increase. An additional benefit will be, the expansion tank also functions as a large water hammer arrestor.

The most appropriate location for the expansion tank, will be Tee'd into the cold water supply line to the water heater. The expansion tank's air pre-charge pressure should equal the PRV setting, so since your PRV is normally set to 60 psi, the pre-charge pressure (with no water within the expansion tank) should also equal 60 psi, so water will enter the tank only when the water pressure exceeds 60 psi, and will be completely drained when the water pressure is reduced back down to 60 psi or below.

 

[kitsune]

Water hammer will occur most frequently when a valve is closed rapidly, but can also occur under certain circumstances when opening a valve.

When cold water is heated, as occurs within a water heater, the water will expand. As water cannot be compressed, even a small amount of expansion when there is no provision to absorb that expansion, will cause the plumbing system static pressure to rise rapidly and significantly.

The PRV on the municipal supply line will act as a one-way valve so the expansion occurring in the WH, cannot push backward through the PRV to the municipal water main, resulting in your home's plumbing pressure rising significantly above the PRV pressure setting.

Hot water usage patterns will influence the amount of pressure rise as will the WH temperature setting. A long shower will result in a greater amount of cold water to be heated, compared to a shorter shower, and hot water use directly before bed, will typically result in elevated pressure throughout the remainder of the night, until any water is again used.

While opening any faucet will cause the additional pressure to be rapidly relieved, that sudden drop in pressure, particularly when the pressure is greatest, maybe causing the PRV to shudder, so it maybe vibrating rapidly, creating shock waves downstream throughout the home's entire plumbing system.

When there is a check valve or PRV located between a WH and a municipal water main, a thermal expansion tank is an absolute necessity. The expansion tank will absorb water expansion, thereby minimizing any resulting pressure increase. An additional benefit will be, the expansion tank also functions as a large water hammer arrestor.

The most appropriate location for the expansion tank, will be Tee'd into the cold water supply line to the water heater. The expansion tank's air pre-charge pressure should equal the PRV setting, so since your PRV is normally set to 60 psi, the pre-charge pressure (with no water within the expansion tank) should also equal 60 psi, so water will enter the tank only when the water pressure exceeds 60 psi, and will be completely drained when the water pressure is reduced back down to 60 psi or below.

Thanks for the informative comment @Bannerman . I just finished the install of an Amtrol ST-5 about a week ago on my 40 gallon water heater tank and do notice that the pressure does not creep up anymore (when the water heater is not on) and is pretty consistent at 55 psi at the main water line.

However I do notice only whenever the water heater does turn on the water pressure at the main water line does go up by 10 psi and no higher (before the thermal expansion tank when the water heater was on or off the pressure would rise 10+ psi up to 20psi), does this mean that the thermal expansion tank is not working or is that to be expected? Because when the water heater is no longer running the main water lines pressure is back to 55 psi. Adding it did lessen the water hammer noise but it was still audible and noticeable, but even then I do think it is a good thing to add as you've explained above.

Also I believe I've figured out what was actually the main cause of the water hammer issue, I have a gate valve on the cold water supply going into the water heater and seemed like that was not fully open or fully closed and every time we would use the toilet or use cold water elsewhere it the water hammer would be heard. So I've turned it all the way open to the max and would still hear a little bit of the water hammer but if I slightly turn it down from max opened the water hammer is non-existent. Also if I completely turn off the gate valve a slightly open it a bit to let the water to flow into the water heater the water hammer is non-existent. I've read online that gate valves should be fully open so I've left it as fully open but slightly turned it down a bit so the noise was nonexistent. I think in the near future I may have to replace that cold water heater gate valve with a ball valve as on the hot side it has a ball valve.

A week later now and I dont hear the water hammer anymore so it's probably a combination of both the thermal expansion tank helping to control the rising water pressure and fully opening the gate valve.

 

[Bannerman]

whenever the water heater does turn on the water pressure at the main water line does go up by 10 psi

During actual hot water use which will cause the the WH to turn on, there should not be any increase in pressure as the water flowing to the shower, faucet or appliance, will be relieving any pressure rise.

The situation discussed earlier, would only occur after hot and cold water consumption has stopped, so expansion of the cold water that entered while hot water was being utilized, would have nowhere to be absorbed or relieved. Now with a thermal expansion tank installed, any water expansion resulting while cold water continues to be heated after water use has stopped, will be absorbed into the expansion tank, thereby limiting pressure rise to a minimal amount.

While the ST-5 has a maximum acceptance volume capacity of 0.9 gallons, it is the recommended model for a 40 gallon tank WH with a temperature setting up to 140 F and supplied with 60 psi water pressure.

Did you adjust the ST-5 air pre-charge pressure appropriately prior to turning on the water?

If the expansion tank is currently pre-charged to a higher pressure such as 70 psi, then no expansion will be absorbed until the pressure exceeds 70 psi.

If the air pre-charge pressure is currently lower such as 50 psi, compared to your 60 psi PRV setting, then some amount of water will always remain within the expansion tank, thereby reducing the capacity that maybe absorbed for expansion while the system pressure exceeds 60 psi.

I have a gate valve on the cold water supply going into the water heater and seemed like that was not fully open or fully closed

A gate valve is superior to a globe valve as a fully open gate will impose lower flow restriction. Unfortunately, over time, the valve's gate can sometimes become disconnected from the valve stem, resulting in the gate partially obstructing flow even as the valve handle has been fully opened.

For the reason mentioned, a full port ball valve would be the preferrable and more reliable option for your application.

 

[kitsune]

While the ST-5 has a maximum acceptance volume capacity of 0.9 gallons, it is the recommended model for a 40 gallon tank WH with a temperature setting up to 140 F and supplied with 60 psi water pressure. Did you adjust the ST-5 air pre-charge pressure appropriately prior to turning on the water?

Hey Bannerman thanks for the informative info. Yeah I set the main water line to 60psi and set the ST-5 air pressure to 60 psi off of the water heater (not attached to the water heater). The change I've noticed is that I do not see pressure creeping up as before it was installed when both hot and cold water usage has stopped. But say when hot water was used then stopped and the water heater turns on to heat up the water that is when I see about a 10psi increase at the main water line.

If I were to check or refill the ST-5 is it better to have it remove off of the water heater to refill with air if it is low or could I fill it up while attached?

 

[Bannerman]

If I were to check or refill the ST-5 is it better to have it remove off of the water heater to refill with air if it is low or could I fill it up while attached?

Keep it attached, but with the water supply shut off, and with a faucet open to allow the tank to drain incase there is any water inside.

But say when hot water was used then stopped and the water heater turns on to heat up the water that is when I see about a 10psi increase at the main water line.

WH's are typically activated during hot water use, but will remain active for some amount of time after hot water use stops, to continue heating the cold water that entered up to the desired temperature. Sometimes, brief hot water use will cause activation to be delayed, but since the amount of cold water that entered will be minimal, the run time will be minimal so the amount of expansion should also be minimal.

The greatest amount of expansion will usually occur when the tank is first installed and filled 100% with cold water, which will then all be heated while no hot water use is likely to occur. Even in this scenario, pressure rise will be gradual as water temperature becomes gradually increased, not a sudden 10 psi increase when the WH becomes activated.

Although I do not recall your hot water temperature being stated, if the usual 120-125F, I anticipate your ST-5 should be sufficient to absorb 100% of the resulting water expansion from heating all 40-gallons.