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Earlier today, I noticed a strange, repetitive clunking noise from the vicinity of my water heater. After some investigation, it seems to come from the cold water supply to the water heater.

Here's what I've found:

  • turning on a faucet quiets the noise temporarily. After shutting off the faucet, it stays quiet for a bit, then the noise comes back.
  • turning off the cold water supply to the heater stops the noise (and the water)
  • the noise occurs while no water is being used in the house.
  • the noise repeatedly clunks about once a second.

Any ideas what this might be? Is it something that needs fixing, or can it be safely ignored?

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maybe something that involves overpressure? –  Asaf Chertkoff Apr 5 '11 at 4:54
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2 Answers

up vote 6 down vote accepted

I had this exact scenario in my home and the culprit turned out to be a failing pressure regulator valve. It's typically installed after the shutoff valve where the line enters the home and will probably have a bolt going into the side of the device that would be used to adjust the pressure.

To see if this is the case, go over to the home improvement store and pickup a water pressure gauge that screws onto a garden faucet. Attach the device to any fixture, open the valve and leave it, then go inside and turn on the cold water for 5 seconds, back off, and go back to the gauge to see if it starts climbing as the pipes bang.

You may also notice toilets or other valves leaking in the house if you have an overpressure situation. I ended up replacing several leaking toilet valves and a sink valve because of pressure issues.

Replacing this can be a DIY job if you're comfortable cutting and soldering pipes.

Edit: here's a sample picture

enter image description here

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i've also thought it is a pressure issue :) –  Asaf Chertkoff Apr 5 '11 at 19:47
@Asaf: I was wondering why you didn't put it as an answer. –  BMitch Apr 5 '11 at 20:09
@B Mitch: cause it was only a speculation :) I didn't had the experience with it to answer a full one, like yours! –  Asaf Chertkoff Apr 5 '11 at 20:24
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It could be / do you notice air coming out of the faucet? Air in the line could cause the clunking. They sell plumbing strapping. Its just metal strapping with holes in it about every half inch? Wrap it around the problem pipe and screw it into the closest 2x4 or joist. It doesn't cost much; they use it solve pipe rattling.

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If your pipes are copper, buy the copper strapping, not the steel. Steel touching copper can lead to corrosion problems. –  Chris Cudmore Apr 5 '11 at 14:50
The pipe is not along the wall. It drops down from the ceiling, loops around, and goes into the water heater. The clunking seems to be internal to the pipe. I'll check for air in the line, though. Thanks. –  Tim Apr 5 '11 at 16:01
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