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Discuss Can I fit more than one mini Water Hammer Arrestor? in the Plumbing Forum area at

  1. Biilee

    Biilee Member

    I'd be grateful for any advice re the following:

    I have a mini water hammer arrestor on the cold feed into my combi boiler, which is situated in the airing cupboard on my house's landing next to the bathroom. Please see the photo.
    The arrestor was fitted when my old gravity central heating system was converted into a combi boiler system by BG. The arrestor was installed by BG to reduce reverberation in the pipes, which occurred when any of the taps (both hot and cold) in the kitchen and bathroom were turned off and to stop water shooting out of the instant shower over the bath (when turning off any of the taps in the bathroom). The arrestor also reduced some (but not all) of the clunking heard when my washing machine (situated in my kitchen downstairs) stops filling and when the toilet cistern in my bathroom stops filling.

    The problem I'd like to solve
    The first mini water hammer arrestor that BG installed only lasted about 2 years before it failed. It was then replaced with an identical one (almost 4 years ago) which initially worked almost as well as the BG one had done. However, just 5 months after installation, the replacement arrestor needed re-inflating. After re-inflation it has worked well to stop water shooting out of my over-the-bath instant shower, but the dampening of the reverberation (caused by taps being turned off and the clunking when my washing machine and toilet cistern stop filling) isn't as good as was achieved by the original BG arrestor.

    I'm reluctant to replace my present mini arrestor as it is currently working well to stop water from shooting out of my shower, so would fitting a second mini water hammer arrestor on the same pipe (just above the existing arrestor) possibly further reduce the reverberation and clunking?

    (I have thought that a water pressure reducing valve might be preferable to fitting another mini arrestor, but it would take a contortionist to get into my kitchen cupboard to fit one on the pipe between the stopcock and the kitchen sink taps.)

    Many thanks in anticipation of any advice anyone can give me.
  2. king of pipes

    king of pipes Trusted Plumber GSR Top Contributor!!

    Not what I would do you could fit a larger vessel and bracketing up that pipework properly will also help . Cheers kop
  3. scott_d

    scott_d Plumber GSR

    Try clipping the pipe first
    Where it's on show and up in the loft (looks like it goes up)
    • Like Like x 1
    • Agree Agree x 1
  4. dancinplumba

    dancinplumba Trusted Plumber GSR

    hi what is the incoming water pressure ?
    • Like Like x 1
  5. Vee

    Vee Plumber GSR

    I’d fit a PRV in addition to the shock arrestor.
    • Like Like x 1
    • Agree Agree x 1
  6. Biilee

    Biilee Member

    Hi, what size of vessel would you suggest and could it be located in the same position as the existing mini arrestor? Thanks.
  7. Biilee

    Biilee Member

    Hi, Thanks for replying. I'm not a plumber - so I don't have a weir gauge - but I have worked out the flow and it's just over 13 litres a minute, which I believe is acceptable.
  8. king of pipes

    king of pipes Trusted Plumber GSR Top Contributor!!

    This is how it should look mate each manufacturer will have their own version , 13 litres on the cold or the hot ?


  9. Biilee

    Biilee Member

    It's 13 litres per min on the cold side. Thanks.
  10. king of pipes

    king of pipes Trusted Plumber GSR Top Contributor!!

    you wont need a pressure reducing valve you are a bit on the low side already 20 + litres a minute at 2- 3 bar is the norm, bracket the pipes up see if that makes a difference . cheers kop
    • Like Like x 1
    • Disagree Disagree x 1
  11. Vee

    Vee Plumber GSR

    Was a pressure reading quoted? Didn’t think flow is what causes water hammer but excess pressure?
    • Agree Agree x 2
  12. Best

    Best Trusted Plumber Top Contributor!!

    Good grief!!! One of the good old boys from the good old forum days! :p
    I thought you had passed on, - so to speak.
    Glad to see your name again dancin. :)
    Edit, - sorry, nothing to do with the thread.
    • Agree Agree x 2
    • Friendly Friendly x 1
  13. chris watkins

    chris watkins Plumber

    it's a reunion:cool:
    • Agree Agree x 1
    • Friendly Friendly x 1
  14. dancinplumba

    dancinplumba Trusted Plumber GSR

    didn't realise this place was still running, thanks for the welcome, still some good ones here I see
    • Like Like x 1
  15. rpm

    rpm Trusted Plumber Top Contributor!!

    Good to see that name again fella. :D
    • Like Like x 1
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