When my washing machine is set to wash a load on hot, the cold water pipe rattles. The pipe is firmly anchored to the wall. The pipe makes a noise like a hose that is half-kinked, like theres an air bubble in it. The noise is coming from the pipe on the wall and not the washing machine itself.

How can I diagnose this problem? Why would a washing machine set to hot use any cold water at all? What would cause my cold water pipe to make this noise?

  • Have you tried to turn off the cold water supply to the washing machine to see if the noise persists?
    – Edwin
    Jan 3, 2014 at 17:17

1 Answer 1


Its called "water hammering". You will need to have a water hammer suppressor installed. You can buy one that simply screws on to the faucet and then you connect your washer hose to it.

You can buy them at your local hardware store such as Home Depot, Lowes, Ace Hardware, or any other hardware store of your choice.

Here is a link to describe the science behind it http://en.wikipedia.org/wiki/Water_hammer

  • I'm familiar with water hammering in the context of having the mains off for a while then turning them back on without a few taps open. Would my washing machine be water hammering because it has an internal valve that is cycling? If I run the washing machine on hot (not warm, full hot) why would it do anything with the cold side?
    – Freiheit
    Jan 3, 2014 at 16:59
  • 1
    The hot/cold water originate from the same point at the main line. With the exception that you hot water goes through a giant tank, known as the water heater. This tank may be arresting the pressure surge on the hot side. Potentially the washer might be using a little bit of cold water. Either way you have a difference in pressure between hot/cold causing a pressure surge. That pressure surge has to go somewhere so it is causing the pipes to bang. Installing the water arrestor will solve your problem. Its about a $15 fix. Jan 3, 2014 at 17:38
  • $10 from Amazon. The part is on its way. It sounds like this is a very common problem, thank you for helping me learn about it!
    – Freiheit
    Jan 3, 2014 at 17:42
  • 1
    Installed a small water hammer arrestor right on the input of the washing machine. Solved the problem right away. Thanks @Bryan Focht
    – Freiheit
    Jan 8, 2014 at 1:49

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