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water hammer

Boston_2 Member Posts: 107
My questions is around water hammer. The new system is relatively quite, for the most part when the system is running there is very little noise. Some small ticking and tinging from a radiator and the occasional bang for a pipe. Just recently a loud bang has developed ( distinctly water hammer) 20 -30 minutes after the system has been off… sometimes it can be even longer. At first I thought it might be normal expansion and contraction, but I am pretty sure it's water hammer. Is that possible? Is there a such thing as delayed water hammer?


  • Kool Rod
    Kool Rod Member Posts: 175

    The late water hammer may be centered at your Hartford loop. Check that a close nipple was used to connect the wet return to the loop. Also check the boiler manufacturer's recommendations as to how far the nipple should be below the water line as see if this was measured /installed correctly. (Also check the installation drawings as to where the design waterline should be located) If the boiler cycle starts out with low water this maybe causing your problems. Do you have a very short wet return?

    At the end of the cycle you might want to be near the boiler and observe the boiler water site gauge and see where water level is when the hammer occurs. Also being close to the loop you should be able to tell if that is where the hammer occurs.
    Here's a link to Dan's discussion on this:


    - Rod
  • JBee_8
    JBee_8 Member Posts: 4

    Try to get the rust and dirty water out of a dirty boiler it will also cause end of cycle banging.
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