You guys know how to fix water hammer?

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dualstow
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You guys know how to fix water hammer?

Post by dualstow » Wed Aug 19, 2020 4:29 pm

You know that noise you sometimes get when you shut off a faucet? A loud rattling.

I followed the steps from google because my dad got old and no longer remembers. :-(

1) Turn off main water valve
2) turn on the highest faucet in your home
3) turn on the lowest faucet. Let it drain, turn it off
4) Open main water valve
5) Let top faucet run and when it's done sputtering, turn it off.

I came upstairs to find green water in the sink with black particles. They didn't tell me about that. Meanwhile, the water hammer persists.
Any ideas?
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sophie
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Re: You guys know how to fix water hammer?

Post by sophie » Wed Aug 19, 2020 4:42 pm

My last apartment had that problem in spades. Believe me I sympathize!

I really don't know what the magic is, but it has to do with problems with old steam pipes & valves that probably have to be replaced. The super in my current building is very attentive to those things, and as a result I have not heard a single knock the whole time I've lived here. In my last place, the super was always telling me he would drain the pipes when I reported the water hammer, but it only worked temporarily if at all.

I was able to minimize the problem by keeping the radiator control on full blast or closed completely. The water hammer would happen only if it was partially open.
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Re: You guys know how to fix water hammer?

Post by dualstow » Wed Aug 19, 2020 4:49 pm

Thanks, Sophie.

Some of the plumbing was redone during our renovation 5+ years ago, but now I'm thinking I've heard the vibrations a long time ago from the laundry machines. It's only the bathroom faucet at the top of the house making the same noise that's new.

Maybe I should get some "arrestors" installed. This sucks. We just had a power outage and power fluctuations. I wonder what's next.
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Tortoise
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Re: You guys know how to fix water hammer?

Post by Tortoise » Wed Aug 19, 2020 5:57 pm

I've read that excessive water pressure can cause water hammer. Might want to check your water pressure, and if it's much higher than 55 psi that might be the culprit.
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I Shrugged
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Re: You guys know how to fix water hammer?

Post by I Shrugged » Wed Aug 19, 2020 6:27 pm

Usually the solution is to have a stub of pipe sticking upwards from a tee in the line. I don't know how long it should be, but I suppose a foot or two would be nice. When the line gets pressurized, that stub will contain trapped air under pressure. It will cushion the shock of shutting off a faucet, that causes the hammering.
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Re: You guys know how to fix water hammer?

Post by Hal » Wed Aug 19, 2020 6:39 pm

I Shrugged wrote:
Wed Aug 19, 2020 6:27 pm
Usually the solution is to have a stub of pipe sticking upwards from a tee in the line. I don't know how long it should be, but I suppose a foot or two would be nice. When the line gets pressurized, that stub will contain trapped air under pressure. It will cushion the shock of shutting off a faucet, that causes the hammering.
https://www.bunnings.com.au/our-range/b ... -arrestors
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I Shrugged
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Re: You guys know how to fix water hammer?

Post by I Shrugged » Wed Aug 19, 2020 6:50 pm

Hal wrote:
Wed Aug 19, 2020 6:39 pm
I Shrugged wrote:
Wed Aug 19, 2020 6:27 pm
Usually the solution is to have a stub of pipe sticking upwards from a tee in the line. I don't know how long it should be, but I suppose a foot or two would be nice. When the line gets pressurized, that stub will contain trapped air under pressure. It will cushion the shock of shutting off a faucet, that causes the hammering.
https://www.bunnings.com.au/our-range/b ... -arrestors
Yes, that's the same thing, only better.
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Re: You guys know how to fix water hammer?

Post by Lonestar » Wed Aug 19, 2020 7:03 pm

I Shrugged wrote:
Wed Aug 19, 2020 6:27 pm
Usually the solution is to have a stub of pipe sticking upwards from a tee in the line. I don't know how long it should be, but I suppose a foot or two would be nice. When the line gets pressurized, that stub will contain trapped air under pressure. It will cushion the shock of shutting off a faucet, that causes the hammering.
I've had success with as little as 6" of vertical pipe. Probably 12" would be better if there is room. The closer to the faucet the better.

I also had good results on a water heater that was hammering by using a small pressure tank (think it was about a 2 gal tank). It was installed the same way on top of a tee right at the water heater.
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Re: You guys know how to fix water hammer?

Post by dualstow » Wed Aug 19, 2020 9:25 pm

Thanks, guys.
Much appreciated.
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Re: You guys know how to fix water hammer?

Post by glennds » Wed Aug 19, 2020 9:38 pm

dualstow wrote:
Wed Aug 19, 2020 4:29 pm
You know that noise you sometimes get when you shut off a faucet? A loud rattling.

I followed the steps from google because my dad got old and no longer remembers. :-(

1) Turn off main water valve
2) turn on the highest faucet in your home
3) turn on the lowest faucet. Let it drain, turn it off
4) Open main water valve
5) Let top faucet run and when it's done sputtering, turn it off.

I came upstairs to find green water in the sink with black particles. They didn't tell me about that. Meanwhile, the water hammer persists.
Any ideas?
Hi, the only differences I was taught from your outlined procedure are the following:
1. Keep the lowest faucet open when you re-open the main. Your summary says you closed it before re-opening the main.
2. Flush all the toilets when the main is closed while the faucets are draining
3. When re-opening the main, do so slowly
4. After re-opening the main and the faucets are finished sputtering and building up flow, start closing the lower faucets first and work your way up to the highest

I think this is obvious, but just to confirm, you are only opening the cold side of the faucets, right?

Is the hammering only happening at one particular sink? If so, you could try closing down the shut off valve under that sink a little bit at a time to see if it helps. Sometimes excessive flow through the shut off valve and supply line can cause hammer. If it's happening at multiple locations, this is probably not the problem.

I don't know if anything I've added is helpful, but hopefully so.
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Re: You guys know how to fix water hammer?

Post by Mark Leavy » Thu Aug 20, 2020 5:59 am

glennds and dualstows procedure is great. But it only works if the plumber put the 12" length of upright extra pipe in the line above the fixture.

What the procedure is doing is draining out any water that was in that pipe so that you have an air bubble up there. That air bubble is your shock absorber to dampen the water hammer. When you shut off the water at the tap, all of the water that is currently moving in the pipe compresses that air bubble which acts like a big spring to absorb the shock - and avoid water hammer.

If you don't have the pipe stubs, the procedure doesn't do anything.
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Re: You guys know how to fix water hammer?

Post by dualstow » Thu Aug 20, 2020 7:28 am

Thanks, guys. I don’t have the pipe stubs.

i would say the vibration is only in the bathroom (top of the house), but now that I think about it, the clotheswasher has been pretty loud at the beginning of the cycle ever since renovation.
The new Freakonomics: Why Are Cities (Still) So Expensive? (Ep. 435)
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