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Navien CH-240 Thumping

I have a CH-240 combo water heater, it has been working fine since installation in 2012, Now it has started to thump when we close the hotwater tap in the sink or the shower. I have read most of the discussions in the forum and didn't see anything on this problem. Just wondering if anyone has had this problem and what to do about it.
Thank you Harold


  • DZoro
    DZoro Member Posts: 1,048
    Has it been cleaned recently?
    Is there a pressure tank installed?
  • Keifer301
    Keifer301 Member Posts: 7
    Water hammer from your water pipes?
    Loose pipe(s) can make water hammer sound like it's coming from the boiler.
    If you can't find the point of cause or reach it, (like a loose pipe inside the shower wall), you could try a "water hammer arrester".
    Loving the fact to be known as an old timer and seeing the changes I have seen.
  • Jamie Hall
    Jamie Hall Member Posts: 23,454
    ^ this. These can be really pesky to find. It's quite possible that some hanger or clamp somewhere has come adrift...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England