Help me fix a water hammer

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rew70

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This house has more issues. I have a water hammer in what sounds like the upstairs wall. However it only happens when the downstairs shower is cut off abruptly.

No access panels to the shower/tub pipes. If you shut the water off slowly, the hammer doesn't happen. I have read a few articles on what's happening, etc. But I am unclear as to how to solve the problem.

The house was built in '84 and has copper pipes. Can I shut off the main water supply into the house, open all faucets and spigots. Then turn the water back on? Will this let the air back into the system to prevent future hammers?

Thanks.
 

GabeS

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There's not supposed to be air in your water pipes. What you are suggesting won't do anything. When you close the valve quickly the high speed water suddenly slams against the closed valve and bounces backwards creating an empty vacuum since air can't come in and replace the empty void, then the negative pressure causes the water to rush back to that empty space. This is my understanding of it at least. Someone correct me if I'm wrong.

They have water hammer arrestors that you can install under your bathroom sink. Also when the plumbing the house it's good to use the least amount of elbows as possible. And use 45 degree fittings instead of 90. Sharp turns can contribute to hammering.

And where the lines come out of the wall, some plumbers put tee's there instead of elbows and continue up in the wall with a 8 or 10 inch piece of copper so there isn't that sharp turn.
 

rew70

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Thanks Gabe, I won't waste the time in draining the system if that's not going to help anything. No other faucet in the house creates the problem except for that downstairs shower.

The sink is a pedestal sink and not sure where I would put an arrester? Would be advisable to install one either under the house on the pipe that feeds that shower or I have also read about ones that attach to the washing machine? The WM is in close proximity to the shower if that makes a difference.

Thanks.

 
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PeteD

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You may want to make sure that your system pressure is not overly high. I can get water hammer hammer at a variety of locations in my hose by shutting things off very abruptly....so I don't do it. If course not everyone in the house follows my lead.

I have a pressure regulator that dials the street pressure of about 93 psi down to some lower level that I can't recall. Too much pressure can lead to problems over time and water hammer is not something you want to have happening on a regular basis. It may cause problems in the long term.

My regulator had failed before and I had 93 psi in my house - too much and the water hammer was ridiculous.

Pete

icemaker_box_pex.jpg
 
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Themp

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When my house was copper plumbed in 84 the plumber put stubs in various locations. When I ask what these were he said they helped for water hammer. He also said to drain the system every so often to let air back in the stub columns as the water will absorb the air over time. I still do this periodically by shutting off the main, opening all the faucets in the house and letting it drain. Then turn the water main back on and then walk around and shut off all the open faucets.

Some folks have told me that these air extensions do nothing, but I do the draining anyway.

Tom

If you have air chambers, that works for a short time. You have nothing to lose by trying
Terry
 
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Jadnashua

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Those air chambers work for only a very short time. The proper way to do this is to use an engineered hammer arrestor. This has a sealed piston or bladder that won't allow the air to be absorbed in the water. An arrestor needs to be close to the valve that is causing the problem or it is unlikely to do much of anything. If the plumber installed stubs near the valve, you might relieve the problems for a short while if you do drain the lines, but it won't last long. Other than the annoyance, the rubbing of the moving pipe against other things can, over time, wear a hole in it and ruin your day. The higher the water pressure in your house, the more likely this is going to happen. You should pick up a gauge and check it. you can get one at a big box store or a plumbing supply shop for around $10. The easiest thing is to screw it onto a hose bib. If it is over 80#, you should probably get a pressure reduction valve, and if you don't have one, an expansion tank for your WH (or it may start to leak after you use a lot of hot water).

mini_resters.jpg

The one on the left is for a washer.
The one in the center can be soldered onto a tee.
The one on the right can be used inline like for a lav supply or an icemaker line. http://www.siouxchief.com/B_Product_Detail.cfm?GroupID=350300
 
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rew70

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Thank you all for the advice. I will go to the local HD and pick up a pressure gauge and go from there.
 

hj

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hammer

Water hammer has nothing to do with creating a vacuum. When the valve closes quickly on moving water, it is like a car hitting a brick wall. Whether there is a noticable sound or not depends on many factors, including how fast the water is moving and how quickly the flow stops. Unless something is installed right at that point to absorb the energy, the hammer will occur. There is a similar thing which can occur in long water lines when a faucet or valve OPENS suddenly. In that case the water cannot start moving fast enough so the pressure drops to zero for a millisecond, and then when the water does start to move it hits that zero pressure zone with an impact that creates a "reverse" water hammer.
 

Terry

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If you have a bathroom lav nearby, you can add hammer arrestors between the shutoff and the supply line.
If the piping is within six feet of the shower, it should help.

 
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vinbar

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I solved a water hammer problem by using hammer arrestors on my washing machine lines. It was a quick and inexpensive fix. My question is, why do I have water hammer and my neighbour doesn't? Our houses are about the same age with a similar floor plan.
 

Jadnashua

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Two possibilities off the top of my head...sloppy workmanship that didn't anchor the pipes or route them well, or they have a pressure reduction valve and you don't. Water hammer is usually only evident when you have a quick acting valve: ice maker, washing machine, humidifier, etc (typically a solinoid valve - electrically controlled valve). So, if they don't have any of those, they may not notice it, eiter.
 

Zxed

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Two possibilities off the top of my head...sloppy workmanship that didn't anchor the pipes or route them well, or they have a pressure reduction valve and you don't. Water hammer is usually only evident when you have a quick acting valve: ice maker, washing machine, humidifier, etc (typically a solinoid valve - electrically controlled valve). So, if they don't have any of those, they may not notice it, eiter.

i would x2 the copper pipes not being anchored..

i am re-doing my master bath whih is direcly above the kitchen., turn off the water abruptly makes the pipes above jump., they are not anchored in yet :)
 

vinbar

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Washing Machine Water Hammer

Thank you for the advice. The new front load washing machine with the quick close solenoids was definitely the culprit. I also have braided fill hoses that seem to be much smaller in diameter than the older rubber hoses. They really jump when the water shuts on and off. Should I use the larger diameter hoses instead? Checking to see if the pipes are fastened properly is going to be a priority as well.
 

hj

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hammer

Water hammer has absolutely NOTHING to do with securing or unsecured pipes. It happens inside the pipe and can occur in any system. An unsecured pipe can create a secondary sound, but that is not the water hammer.
 

Jadnashua

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Sometimes we get a little loose with the terms...moving water has inertia...when you try to stop it, that kinetic energy has to be disipated. It can act like a piston or hammer and functionally act like it hits with a hammer, or it can move the pipe and actually hit something (probably not technically a water hammer - call it pipe banging, or pipe hammer?!). In both cases, you are disipating energy and can damage things. Both can be confused for the other. Strapping the pipes so they don't bang into things solves one part, a hammer arrestor does the other. Both parts of this may be required to solve a noise problem. If the pipes move when you shut off a valve, strapping may not be enough to prevent damage in the long run.
 
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