HELP! Banging Radiator

Discussion in 'Plumbers' Talk' started by Kelly O'Flaherty, Jan 11, 2018.

  1. Kelly O'Flaherty

    Kelly O'Flaherty New Member

    Hi all!
    First time posting - really hoping someone can help me.

    When we turn on our central heating there is an loud banging noise from near the radiator in the main bedroom. It's not just when the heating is turned on or off/cooling down, it's ongoing.
    It's driving me mental!
    I've tried everything - we have an old boiler and initially looked at that as the issue, had someone come and service it and despite it's age/being a tad loud it's fine and not the cause of the noise. It's been given the all clear.
    It's not trapped air as when I bleed the radiator very little comes out before the water starts to flow out.
    The other radiators in the house are dead silent... it's just the one in the bedroom, but you can even hear the banging noise if you're in the room under the bedroom!
    I then thought it was loose pipes knocking against the joints as they expand/contract - so plagued my OH to pull up the carpet, move the furnishings and lag/wrap the pipes where they meet the joints to tighten it all up.
    He's just done that with his Dad...and low and behold....the banging continues!

    It's the only loud one in the house, it's an old radiator, quite old. It was in the house when we bought it - will replacing it make any difference? Will that solve the problem?
    The only other thing I can think of is power flushing the central heating system...but I'd rather try everything else before having to resort to that.

    ANY HELP is much appreciated. Please save my sanity before this knocking drives me over the edge!

  2. kiaora

    kiaora Guest

    When you bleed the radiator, you may not be getting the air out!

    You will have a flow and return pipe, with two valves each side of radiator.

    Often what can happen is to get air in one of the pipes, and when you open the vent, the water flows from the pipe with no air, and leave the other with still air in it.

    To deal with this, turn off both valves, open vent and hold bowl to air vent, ( a little help needed here)

    Open one valve, and draw the water up one pipe, then repeat, closing the first valve and opening the other valve.

    Hope this helps
  3. Tricky Dicky

    Tricky Dicky Screwfix Select

    Turn off this rad using the handwheel, also the lockshield (count the number of turns to lock it down).
    Does the banging cease ?
    If so we can move onto stage 2.
    kiaora likes this.
  4. kiaora

    kiaora Guest

    Good advice !
  5. Kelly O'Flaherty

    Kelly O'Flaherty New Member

    Thank you both!
    I’ll have my OH & his Dad try both of the above.

    I’ve tried turning it off to see if it stops banging...alas it’s so old the handwheel doesn’t seem to do anything/ever stop turning.
    Hence why I’m wondering if a new one would help the problem.
    I’ll see if they can turn it off in a more crude/manual way by lifting off the handwheel and turning it off with a spanner.

    Any other advice/suggestions also welcome! Happy to plague OH to try everything to stop the noise!

  6. chippie244

    chippie244 Super Member

    Drum and bass init :p:p
    nigel willson likes this.
  7. Sheelin

    Sheelin New Member

    Do you have a TRV on the rad? These can sometimes cause the symptoms you describe.
  8. chuzzwuzzer

    chuzzwuzzer Member

    I'm having the same issue as the original poster. Knocking driving me nuts and finally worked out is was coming from the rad in the hall. I've tried the above advice. Turned the thermostatic valve off and also the lockshield valve. Knocking stops. Tried bleeding.No air coming out. Tried turning on thermostatic end and bleed air coming out. Closed this valve and opened other valve and bleed. No air. Turn both valves on and a couple of hours later knocking starts again. Any advice ?
  9. Wayners

    Wayners Screwfix Select

    Not sure if this is what you are hearing but... Where the rad sits on metal bracket causes a noise as it heats and cools. Rad should sit on plastic gromit but this falls apart or is not fitted. Plastic gromit means it slides a little. It's more a ting ting noise. Vasiline or something temporary fixes sometimes
  10. chuzzwuzzer

    chuzzwuzzer Member

    Dont think thats the problem.Sounds more like someone is banging the pipes but its not constant. It will happen randomly and do it 5 or so times then stop for a while then does it again
  11. Wayners

    Wayners Screwfix Select

    Drop rad and put new valves on. Some valves used to have a flow direction (in and out) with arrow on the chrome valve side but most I've fitted are both directions now, however back in the day if you got the flows wrong through the valve it would hammer. I'm thinking your valves are correct but crud inside is causing this hammer noise so swap for new. Easy enough job if you can bung up tank to create a sealed system to save draining down system
  12. pra

    pra New Member

    " Dont think thats the problem.Sounds more like someone is banging the pipes but its not constant. It will happen randomly and do it 5 or so times then stop for a while then does it again "

    Is this a different proroblem to an individual radiator vibrating for a couple of minutes, then dying away ? Not always the same one, and if I can be bothered getting up, then slightly altering the thermostatic valve stops it straight away.
  13. Dolly40

    Dolly40 New Member

    I’m having same problem, had the plastic inserts and made slightly worse if anything. Could this problem be anything to do with MagnaClean system which I see on my boiler was fitted over 10 years ago? Any help appreciated. The noise definitely sounds as though it’s from radiators and has affected 4 of the 7 in my house that I moved to 2 years ago
  14. AnonymousRadiator

    AnonymousRadiator New Member

    I have the exact same problem. It’s driving me mad but I just can’t find a solution.

    Bled the radiator today but there was no air at all. Will try some of these tips tomorrow if I can.
  15. kiaora

    kiaora Guest

    This problem can occur if the radiator valve are not the type that allow flow both ways, and if fitted the ‘wrong” way, you get this nocking sound,

    To check this out, look at trv, and see if it’s marked with an arrow or a two he headed arrow!

    Good luck

  16. KIAB

    KIAB Super Member

    Most of the newer valves, bi-directional.


    Older valves,direction of flow.

  17. MGW

    MGW Screwfix Select

    That was also my thoughts, early days people fitted non bi-directional and also never bothered with by-pass valves, valve should be on supply side where possible, as it starts to detect heat from radiators faster so less likely to over shoot, but old valves were well known for banging if flow reversed.
    KIAB likes this.
  18. andy48

    andy48 Screwfix Select

    Some cheap thermostatic valves cause this problem no matter which side they are fitted.
  19. didox

    didox New Member

    I appear to have the same problem. Just one radiator and bangs when heating comes on or goes off. Banging is loud, I wouldn't mind too much but it is my bedroom and it wakes me up everytime the heating cycles on or off. Is it likely to be the TRV or the value at other end (sorry no idea what it is called)? I don't suppose anyone could recommend someone in the northeast (Sunderland) who could sort it for me?
  20. didox

    didox New Member

    I have looked at both ends of the radiator and cannot see any arrows, neither single or double headed ones. Any help appreciated.

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