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Pipes bang bad when turning water ON

Discussion in 'Plumbing and Central Heating' started by Albopalbo, 25 Jan 2021.

  1. Albopalbo

    Albopalbo

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    Location:
    Norfolk
    Country:
    United Kingdom
    Some help diagnosing how to fix this would be appreciated. (new build house)

    About a month ago we had a plumber install a shock arrestor to our washing machine supply as it was banging when the water shut of abruptly. Issue fixed, but ever since then another issue has popped up:

    When we turn ON the cold tap in the kitchen, or bathroom the pipes bang badly. The initial flow of water for 1 second is super pressured then flows normal. If I watch the pressure indicator and turn off the tap, the pressure slowly rises from 3.5 to 5 over about 30 seconds. Turn on tap, BANG, pressure drops to 3.
    I initially thought it may be some air trapped in the pipes from the plumber draining the system, which was slowly getting compressed by the mains pressure, then causing a water hammer when the flow was released so I drained the system again and filled it by opening the upstairs taps. Still bangs. I repeated, this time opening the upstairs taps in a different order. No joy.

    Am I right in my assumption? How do I go about sorting it? Or is this caused by something else. It never did it before the plumber drained the system..? Confused.

    Many thanks
     
    Last edited: 25 Jan 2021
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  3. rbranco

    rbranco

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    you might need a PRV?
     
  4. Albopalbo

    Albopalbo

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    Location:
    Norfolk
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    I've had an investigate and there is a PRV installed. Tried turning it down and had to turn many many times before any difference was made. Now I've set it super low to about 1 bar, the kitchen taps a dribble, but when I turn the tap off, the pressure slowly creeps up to 6-7bar over 15mins. Faulty PRV?
     
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