Whole house water hammer

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theitguy

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Hello,

I am looking for advice. I am experiencing major water hammering issue near what I would consider the end of the system in my house where two upstairs bathrooms share a common wall. The hammering sound is happening on both hot and cold sides. The hammering can be triggered by almost any faucet or appliance in the house, upstairs or down; for example, the hammering sound is happening in the same place upstairs, if you are running the washing machine downstairs.


A little backstory:

We recently remodeled both bathrooms and replaced the shower values with new Moen valves. One of the showers used to have minor hammering when moving the lever from cold to hot, but this was minor, and no other fixtures or appliances in the house triggered any sort of hammering. The issue started after we replaced the valves, but I couldn’t tell you if it was exactly right after or shortly after replacement.


What I’ve tried so far:

· I’ve secured all pipes with pipe straps and shims in the entire house. No pipes are moving at this point. I even secured the water heater.

· I installed Sioux Chief mini arrestors on the upstairs toilets – no effect

· I installed a Sioux Chief mini arrestor on the riser running from the 1st to 2nd floor – no effect

· I checked the water pressure in the system – the pressure is in normal residential ranges

· Countless draining / refilling on the system to attempt to recharge air columns

· Checked for water logged air columns– those all seemed good, but I did not check the upstairs shower columns. The showers are the last outlets in the system.


Since the hammer is affecting the entire system, my current guess of why this is happening is because the pressure in the system drops when a faucet is being used, then recharges too quickly and bangs at the end of the system. Is this guess correct?

Is this something anyone has come across before or have any ideas on how to resolve?
 

Jadnashua

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A water hammer occurs when you stop the flow...inertia of the water wants to keep that flow going, and when it hits a closed valve...that energy is transferred to the pipes and can literally hammer it into something. If it's happening throughout the house with any flow all of the time while they are running (not just when you shut something off), it's more likely a shutoff valve with a washer that is loose. The flow moves the washer, shutting water off, it falls back, letting water flow, and repeats itself. It can happen fast enough so that it's hard to tell the flow is fluctuating. Make sure that the main shutoff is fully open and test that it actually shuts off. This typically would only apply to a valve you have to twist open or closed. The better choice for this shutoff would be a full-port ball valve that doesn't have a conventional washer and a seat.

Does this happen with no flow? If you have a closed system and do not have an expansion tank (or the tank has failed), the expanding water can sometimes 'jump' past the check valve when the pressure rises, then it shuts again. You might want to buy a pressure gauge and watch it while the noise is occurring. IF it's spiking, that can be informative.

Do you have a pressure reduction valve (PRV) in the house? That might be the source of the problem. Less common, is some debris in the line that is bouncing around, acting like a plug, similar to a fluttering washer. Then again, it could be something else I'm not familiar with.
 

theitguy

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Thanks for your reply. The noise only happens when shutting off a faucet, toilet stops filling, etc. One thing I have noticed is that if I have two faucets running on the same line (cold or hot), and I shut off one of the faucets, the hammering does not happen. Shut off the second faucet and it will.

I do not have a pressure reduction valve in the house.

If there isdebris in the line, what would be the best way to flush it out? Could I remove the valve stems of my upstairs showers and run the water through?
 
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