Water hammer driving me nuts

Discussion in 'Plumbers' Talk' started by AndrewMB, Nov 24, 2017.

  1. AndrewMB

    AndrewMB New Member

    Good evening,

    Firstly, I am not knowledgeable in the complexities of plumbing and only have a grasp on common sense.

    My partner and I moved into her parents house after her mum died. There was no central heating so we had it fitted recently.

    The banging coming (I think) from the pipes is driving me mad.

    The boiler is in the kitchen. The bathroom is downstairs. And we have three rads upstairs.

    Even with nothing running, no washing machine on, no taps running and no toilet being flushed the pipes will bang. It is a horrible clanking noise. And is seemingly intermittent.

    It is loudest from in the bathroom. And from there it sounds like it is coming from the left, which is the kitchen and also where the cold water main valve is. (Hope I'm using the correct terminology).

    I contacted the guy who fitted the system who wasn't very interested but did come round. He went into the bathroom, flushed the toilet and turned on and off the taps but it did not happen. Typical.

    He then went into the kitchen and turned on the cold tap and said the pressure seems a little high, went into the cupboard where the main water valve is and turned it down. See how that goes he said.

    Within 10 minutes of leaving it was happening again. I contacted him again.

    He told me to check if there was any air in the upstairs rads. I did. There was a little bit of air in two out of the three rads. I bled them til water was present and checked all of the rads up and down. No air in any of them.

    The banging persists.

    I then did some reading and noticed the boiler pressure was set to about 1.9. After reading it generally should be around 1.0 to 1.5 and confirming that in the instruction manual I bled a rad until it dropped to 1.5 which it is currently.

    The banging persists. It's happening now as I type this. Nothing is calling for water other than the central heating being on.

    I recorded the noise on my phone and there were 5 bangs in a little over a minute. And I'm sure when i was in the kitchen I heard the boiler flame up and immediately after there was a bang.

    I also sat under the kitchen sink with my hand on the hot and cold pipes running along the kitchen and when the bang happened I certainly felt it.

    I don't know what to do next. The guy who installed it is not giving me much confidence and is not replying to me now.

    The pipework to the rads is new (as there was none prior, not having central heating) but the other pipework is probably the original pipework or at least old.

    Can anyone suggest anything I can try or check but please bear in mind I have no expertise at all in this area.

    Please. Please. Help us. We are having everything done to the house to make it perfect for us and spoiling it is this persistent and horrible clanking noise.

    Many kind regards

    A hopeful Andrew.
  2. Sorry for the delay in replying, but I was incapacitated by you saying the banging was driving your nuts.


    Any chance of putting the sound clip on here, or on Youtube for example?

    Anyhoo, you seem to understand more than your plumber. Yes, 1.9 bar is a wee bit high for a sealed system pressure - it ain't 'bad' as such, but is unnecessary, so 1 to 1.2-ish bar is usually fine for a one storey hoosie.

    Anyhoo, that didn't fix it. Which is no great surprise.

    Ok, if your mains pressure is excessively high - say 4 bar and upwards - then your house would almost certainly appreciate it being tweaked down to say 3 bar or slightly over. Guess what? Turning your stopcock down will not affect your static pressure, so your plumber is a bit of a chancer.

    To give the guy a wee break, if he didn't actually hear the banging, then there isn't much he can respond to. Having said that, he also didn't seem that bothered about sorting it anyway. But, until he hears it, he won't know what to act on (some people will declare a wee 'creak' is a loud 'bang', for example).

    Bottom line, tho', your installer is responsible for sorting this. But he needs to hear the sound.

    Do you have a hot cylinder, or is it a combi boiler?
  3. KIAB

    KIAB Well-Known Member

    Deleted member 33931 likes this.
  4. AndrewMB

    AndrewMB New Member

    Lol Thanks for reply. I have uploaded the clip:

    And he listened to it so although he never heard it when he was here, he did hear the clip.

    How do I know what the mains pressure is? Are you referring to the main water valve that he turned down? How is that pressure measured?

    It is a combi boiler. The tank was removed from upstairs during the install.
  5. AndrewMB

    AndrewMB New Member

    Where do this go? Like I said, I'm ignorant when it comes to plumbing. And how do identify unsupported pipework? Do I literally need access to all the piping to check that? I' having a new bathroom and kitchen fitted over the next month or so, so that would be an ideal opportunity. And the main reason I wanted this sorting... before having a new kitchen and bathroom fitted.
  6. KIAB

    KIAB Well-Known Member

    The cold water main valve as you call it, is your main stopcock, this can wear with age, seize up,etc, so replacing it with a full bore lever valve is better.

    As to unsupported pipework, some of it might not have pipe clips so can move about a bit.
    Also, as your having a new central heating system, lag the pipe, pointless heating the void under the floorboards.
  7. terrymac

    terrymac Well-Known Member

    Andrew do you hear those sounds only when your central heating is on ,or do you hear them when its off and rads are cold ? To establish if its c/heating related or if its your house plumbing ,the next time you start to hear it ,quickly close down your main stopcock to see if it stops it dead. If it does then your domestic plumbing is the source, as opposed to c/h . difficult to make out listening to your audio post ,but it sounds to me like flow interruption .check your toilet cistern .if water level is dropping in cistern because it can escape from cistern into pan ,then the filling valve may be opening and closing repeatedly / intermittently.
  8. AndrewMB

    AndrewMB New Member

    Thanks for reply.

    Firstly, the heating hasn' been off since we had it installed. My partner feels the cold more than I do. I think this is somewhat to do with the coldness in her heart and soul but this is just a theory.

    Next time it happens I will switch the water off at the mains.

    It' funny you should mention the toilet and I haven' even thought about it until now...

    Our flush of late isn't working correctly. I think a seal has gone inside because we don't get a full flush any more. I've just checked it again. When flushed the cistern only empties to just below half then a gurgling sound happens and it stops flushing and starts to fill again. Not sure if that's connected.

    I haven't gone about fixing that because in the next week or two we are fitting a new bathroom.
  9. terrymac

    terrymac Well-Known Member

    The flush not working properly is not the cause of the noise . but when it fills up and the float valve closes ,a few minutes after the flushing ,that is when you can sometimes hear a clunck.if the water level then very slowly drops ,if a seal has failed ,then the valve will open again and tank water level will top up and again the valve closes.this will then continually happen and may be the sound you hear each time the valve closes. I have listened several times to your audio and can't make my mind up if its water hammer or CH pipes expanding / contracting and rubbing against or banging against another pipe or something else.
  10. KIAB

    KIAB Well-Known Member

    CH has been off the whole time.
  11. fostyrob

    fostyrob Active Member

    Been on the whole time. He says it hasn't been off.
  12. AndrewMB

    AndrewMB New Member

    CH has been on the whole time
  13. AndrewMB

    AndrewMB New Member

    Ok so maybe not that then. The cistern level doesn' drop. And I suppose when I take the kitchen out that will be the time to check for loose pipes. Same with the bathroom.

    So frustrating.

    As it stands should I lower the pressure to 1.2?
  14. fostyrob

    fostyrob Active Member

    You might not know as you didn't install the system but as has been said it could be down to expansion. If a pipe has been notched through a joist and the whole it a little on the tight side it may creak/bang.
  15. fostyrob

    fostyrob Active Member

    That should be hole and not whole!
  16. fostyrob

    fostyrob Active Member

    Can you localise the banging to anyone room/area or is it throughout the house?
  17. AndrewMB

    AndrewMB New Member

    When I'm in the front room it sounds like it's coming from the kitchen / bathroom. Both are next to each other. When I'm in the bathroom it sounds like it's in the kitchen. I've never really noticed it upstairs.
  18. AndrewMB

    AndrewMB New Member

    If the upstairs tank was removed I wonder where that pipe/s were capped off? Could that be worth asking?
  19. KIAB

    KIAB Well-Known Member


    Misread OP's post.
  20. fostyrob

    fostyrob Active Member

    Would start in the kitchen as ot sounds like the most obvious source.

    Apologies if you have said but where is the rising main (where the water enters the house) and where is the boiler?

    You said you can feel the knock through the pipes. Is that the cold water supply or tje central heating pipes?
    Paul12345 likes this.

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