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Water hammer, and arrestors don't work

I have a real water hammer problem, and the arrestors I've installed aren't working. I have a newer bathroom in my basement, below the bathroom in the floor above. I first noticed it soon after we installed a front loading washer. I hear the hammer in the ceiling above the basement bathroom (all the pipes I can see are well secured). I can make the hammer go away if I drain the system, but it always comes back. And -- here's where it gets weird -- if I shut off either the hot or cold water valve that feeds the basement shower, the hammer goes away completely. My plumber installed hammer arrestors above the shower -- didn't work. I also put them where the washer connects, no help. My plumber is stumped. He seems to think that a pipe isn't secured properly. But that doesn't explain why closing the hot or cold water valve to the shower stops the hammer. Help! Thanks in advance... Brian.

Timothy Miller
Re: Water hammer, and arrestors don't work

Howdy did the plumber check the psi in your system? Do you have a pressure regulator on the line and is it set at 45 pis?

Re: Water hammer, and arrestors don't work

Water hammer is caused by the inertia of the water in the pipes making the water want to keep moving when a valve (like your washing machine) suddenly shuts. It's kind of like having a concrete Jersey barrier dropped in front of your car when you're tooling down the freeway. The shock will travel back through the pipes and will be absorbed by either pipe expansion or movement.

I'm guessing that the pipes going to the basement shower aren't securely fastened to the building structure past the shutoff valves.

If the static pressure (no faucets open) is greater than 50 PSI, installing a pressure regulator set between 40 and 50 PSI should help. You could also install expansion tanks -- like those used on water heaters -- as a massive shock arrestor on the lines near the washing machine.

Re: Water hammer, and arrestors don't work

Hi. It's been awhile since I posted about this problem I'm still having. I have more info. We just finished renovating our main bathroom upstairs (complete reno.. moved toilet, new shower). We still have the water hammer problem I described a couple years ago. The plumber installed a big tank at the water heater, thinking this might alleviate the problem. Nope. He also thought that the water pressure might be too high. It was a 60.... he brought it down to 40 (adjusting the pressure regulator). Still have the hammer, and now unacceptably low water pressure throughout the house (I'm going to have him bring it back up to 60). Also, during the reno, we opened up the ceiling in the downstairs bathroom where we think we hear the hammer. All pipes are secured very well.

We can still make the hammer go away completely if we turn off either the hot or cold water valves that go to the downstairs shower.

So to date, here's what we've done:

-- Installed arrestors in cold and hot water lines near the downstairs shower -- didn't work
-- Installed arrestors at the washing machine -- didn't work
-- Installed large expansion tank at the hot water heater (hot) -- didn't work
-- Lower pressure from 60 to 40 -- didn't work

We can make the hammer go away if we drain the system, but it comes back in a few days.

I'm really starting to think this is an intractable problem with no solution. I sure hope not. Does anyone have an insights? Thanks... Brian

Re: Water hammer, and arrestors don't work

Could the pipes going down the wall to the shower valve be unsecured?

Re: Water hammer, and arrestors don't work

We opened the wall where the shower pipes are a few months ago to check. The pipes going to shower are very secure. The hammer isn't there.... we hear it above the ceiling in our downstairs bathroom. And the pipes up there are secure... we opened the ceiling last month to check.

This continues to baffle us all.

Re: Water hammer, and arrestors don't work

Hi--I read your problem, and the responses by others; it sounds as though you've tried most of the obvious solutions to no avail. Have you checked with your city's water department for possible causes/solutions? They may have a fix in mind, or can suggest possible ways to work around this problem. Does your city have a water tower that supplies your dwelling, and are you close to it? Rich Trethewey described the opposite problem during a home visit, where the homeowner was so far away from the tower that he had poor pressure issues. In your case, you may be so close that not much of what you do can do will affect the hammer problem; again, check with your city's water engineers for help. They may know of a pump in their system that's boosting city water pressure which indirectly affects you. Are you the only household in your neighborhood with this problem, or are your neighbors similarly affected? Also, check with your local plumbing supply house; they may be familiar with this pressure problem and can steer you in the right direction.

Check these resources out, and good luck.

Bay Area..Ca
Re: Water hammer, and arrestors don't work

if turning off the hot and cold supply to a shower valve eliminates the problem,maybe you should rebuild the valve with new parts to see if that helps.

Re: Water hammer, and arrestors don't work

Did you ever get this resolved? I have a similar problem that I just posted in the bathroom discussion. We have a remodeled shower and if I turn off the water at the shower valve, either hot or cold, the water hammer stops.

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