Plumbing – this clunking noise in the water pipe


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?

Best Answer

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

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