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Question DetailsAsked on 1/5/2012

I have loud water hammer when running dishwasher, washing machine, or shower. The plumber "fixed" it, but it still does it. Suggestions?

The plumber installed an overflow tank in the basement to relieve the pressure, but it did not stop the water hammer. I heard this was not good for the pipes, and it's very loud and scares the tar out of me when it sounds. Looking for a plumber that knows something about water hammer, and CAN fix it. Thank you!

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4 Answers


1). It could be that water pipes are not braced behind the wall
2). It could be air chambers were not installed per fixture.
3). If your lucky the easiest fix is adjusting a problematic angle stop.

Mcdonagh & Sons Plumbing & Sewer Inc.

Answered 8 years ago by


This is usually caused by one of two things or a combination of the two. First, and most likely, is air that rises to the top of the pipes and causes the water to pulse, resulting in the sound you are hearing. A plumber will be able to install arrestors at the valves which will alleviate this. It requires cutting the wall to access the pipes at the shower and you'll have to have someone go in afterwards to patch that up. For the dishwasher and washing machine you can use an in-line unit that you can install youself. It screwes between the valves and hoses.

Solder as needed for shower:

Screw on as needed for washing machine:

The second possibility is the heat in the pipes. If they were not properly insulated they can ping just as a car exhaust does after you shut off the engine. It is the metal pipe cooling down after expanding from the heat of the hot water running through it. Try turning your water heater down. It may not eliminate the sound but should reduce it. Recommended setting is 115-120 degrees for adequate hot water. Higher than that reduces the life of the heater. If you dodn't get enough hot water at that temperature for your average use you may have too small of a heater.

Todd Shell
Todd's Home Services

Answered 8 years ago by Todd's Home Services


Is it possible that the "overflow tank" you mention could be an expansion tank? An expansion tank does allow pressure to expand into the tank, but you should have a Pressure Reducing Valve installed to reduce the pressure coming into your home. This valve would be installed in your yard near the meter.

You are right that water hammer is damaging to pipes, as well as fixtures such as water heaters, due to the high pressure in the pipes. Try to locate a licensed plumber who will discuss a Pressure Reducing Valve with you.

Good luck!

Dixie Bishop
Texas Plumbing Diagnostics
San Antonio, TX

Answered 8 years ago by DixieBishop


great advice above what you hear is air hammer. Any thing that has a solonoid and even a quick closing faucet you get a loud bang in the pipes.

Answered 8 years ago by owen klaus

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