Bad shower valve causing water hammer?

[PatK]

I have had an issue with water pipe hammering for a number of weeks and can't get it to stop.

I had my shower replaced about a year ago. Up until a couple weeks ago, there was no issue with hammering. Now, it has gotten really bad. I added pipe insulation all over the place, added and tightened hangers, and other odd items to try to secure pipes and still the hammering happens.

I have found one strange issue though. If I turn of the hot water valve to the shower, the hammer goes away. My house doesn't really have any water arrestors installed, so I thought that could be the problem. I started with the hot water leading into the shower valve. After cutting into the hot water pipe, which is pex, above the valve, I noticed there was water still coming down from the valve even though the shower valve was shut off.

SO, why was cold water running down through the hot water valve? Is there something wrong with the shower valve not closing? Would this cause the water hammer?

Thanks for your help!

 

[Tuttles Revenge]

what scenario causes the "Water Hammer"? Is it more of a Vibration while the water is running or is it a Kathunk (true water hammer) when you shut off the flow to the shower?

Water coming out from the hot side when you have cut the line and have the water turned off could just be residual. Could be draining from the shower riser. Could be water bypassing the pressure balance shuttlecock.

 

[Sponsor]

 

[PatK]

what scenario causes the "Water Hammer"? Is it more of a Vibration while the water is running or is it a Kathunk (true water hammer) when you shut off the flow to the shower?

It's the Kathunk. I'd describe it as KATHUNK! - buzz - buzz - buzz - buzz. It happens a little when the valve opens, but the bad one is when you shut off the hot water - any hot water: kitchen sink, bathroom sink, shower, etc. It sometimes happens too when shutting off cold water, but not all the time.

 

[Jadnashua]

Check your water pressure. Water hammer gets worse when the pressure is too high. Higher pressure causes, or allows, the water to flow faster through the pipes. WHen you shut a valve off, that higher velocity translates into higher inertia, which is like the difference between walking into a wall versus running into one.

If you have a pressure reduction valve, it may be failing. Or, your utility company may have changed pumps to accommodate some new construction (more homes) or just upgraded their system.

If you have an expansion tank, check the precharge air pressure and verify that it is not waterlogged (failed).

FWIW, there are a few shower valve models that specifically call for installing hammer arrestors as part of the process. Most don't shut off fast enough to cause a hammering, but a few do.

 

[PatK]

Check your water pressure. Water hammer gets worse when the pressure is too high. Higher pressure causes, or allows, the water to flow faster through the pipes. WHen you shut a valve off, that higher velocity translates into higher inertia, which is like the difference between walking into a wall versus running into one.

If you have a pressure reduction valve, it may be failing. Or, your utility company may have changed pumps to accommodate some new construction (more homes) or just upgraded their system.

If you have an expansion tank, check the precharge air pressure and verify that it is not waterlogged (failed).

FWIW, there are a few shower valve models that specifically call for installing hammer arrestors as part of the process. Most don't shut off fast enough to cause a hammering, but a few do.

I was finally able to get an answer from the city. My water pressure is 61 PSI. The city said they aim to have pressure at 55-65 psi.

Is this too high? Also, I'm not sure I can adjust the pressure in my house. I need to inspect the line a little more closely.

 

[Tuttles Revenge]

Up to 80PSI is considered safe for not destroying fixtures/valves/faucets. 60 is just around the sweet spot of good pressure in my opinion.

 

[PatK]

I think I'm going to draw an amateur schematic of my piping. The only constant I can find is that when I shut off the hot water to the shower, the hammer stops. Once I do that, I can flush any toilet and open any valve without the hammer occurring.

 

[Jeff H Young]

I think I'm going to draw an amateur schematic of my piping. The only constant I can find is that when I shut off the hot water to the shower, the hammer stops. Once I do that, I can flush any toilet and open any valve without the hammer occurring.

you have a valve right at your shower to turn off? based on your info the problem is on other side of valve . I dont know if this valve is a stop on the valve or 40 foot away but somewhere after the valve seems to me

 

[Reach4]

Water heaters often have a gadget called a "heat trap". They can generate noise. I don't know if that could be the cause of what you hear. I suggest you put the two bolded terms into a search.