Bang from pipes when turning on water

Discussion in 'Plumbers' Talk' started by Roger91, Jun 20, 2022.

  1. Roger91

    Roger91 New Member


    I know this has been covered a lot elsewhere - I've used previous answers on here to help me get to this stage - but I was hoping for some advice on where to go next. We've had some 'water hammer' type issues that I've been trying to deal with. Our setup is a combi system with copper pipes throughout. We have high water pressure coming into the house at about 6 bar. So far have:
    • Installed a pressure reducing valve just after the stop cock to reduce incoming pressure to 3 bar
    • Added 2 x 24l potable expansion vessels in the space under the bath for both the hot and cold water
    • Put a water hammer arrestor by the washing machine inlet
    This has done a good job of stopping the pipes banging when turning off the taps - but we still get a single bang/knock sound from the pipes when switching some taps on. If I drain and refill the system it seems to cure the problem - but then it comes back after about a day, worse for some taps than others.

    Any ideas why this might be? Is it time to start knocking into walls to check the pipes are clipped properly (this will upset the wife) or am I just being cack-handed refilling the system maybe? As looking on the web, most results regarding solutions for a bang when turning taps on suggest it's air trapped in the pipes.

    Any pointers much appreciated!
  2. Notnowvicar

    Notnowvicar Active Member

    I had this on a system and fitted a mechanical arrester by the worst tap, was the kitchen as it came down from the bathroom..BES supplied mine about 25 ish quid but screwfix do a american one, sioux as I remember.
  3. Roger91

    Roger91 New Member

    Cheers I will give this a try! I've got one of those on the washing machine, but that is by no means the worst thing affected - it's the cloakroom tap coming down from the bathroom actually..

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