Banging Cold Water Pipe

[nrestell]

Hi,

I am hoping for some help before I go mad!

I have a banging pipe that occurs seemingly randomly - it is usually at night and usually between 6pm and 11pm - it can happen at other times but this is much rarer.

I have narrowed it down to be the cold water pipe - you can feel it vibrate if you touch the pipe just after the internal stop tap, just under the sink or just by the combi boiler.

The weird thing is that I cannot isolate what causes the banging to occur. It can happen when no-one is drawing water (no taps in use, dishwasher off, washing machine off, toilet not in use).

It can usually be stopped by turning a tap on and off multiple times.

It can also be stopped by turning off the water (internal stop tap) and turning it back on again. Sometimes, however, it continues after turning the stop tap back on again.

Sometimes it goes on for only a few seconds (20-30) and stops itself, sometimes it goes on for minutes and I have to run a tap/use stop tap to get it to stop.

I have had a plumber change a faulty tap and replace the toilet ballcock (and float) after thinking it could be one of these but to no avail.

Does anyone have any ideas as to what to check next please?

 

[CBW]

I would be looking towards the stopcock, it could be a loose jumper, failing that it can occur if your incoming supply is copper and a neighbouring property has a defect and the noise is travelling.

 

[nrestell]

I would be looking towards the stopcock, it could be a loose jumper, failing that it can occur if your incoming supply is copper and a neighbouring property has a defect and the noise is travelling.

Hi,
Thanks for the response.
Is there a way to determine between the two? For example, if I turn my water off tonight and it doesn't happen does it point to either option more than the other?
Thanks.

 

[CBW]

If you turn your water off and it doesn’t do it I would suspect the jumper, but that’s not to say that if it’s noise transference, it won’t happen. You can only try.

 

[HERTS P&D]

Do you have any push button toilets? Are they slowly leaky into the bowl?

Andy

 

[Alec_t]

I had a similar water-hammer problem recently. Cured by replacing the rubber seal in the inlet ball-valve of the cold water storage tank in the loft.

 

[HERTS P&D]

Does not apply Alec, the OP has a combi but otherwise its a good shout.

Andy

 

[nrestell]

Do you have any push button toilets? Are they slowly leaky into the bowl?

Andy

Hi
No, no push button toilets. Only the one toilet with normal handle flush.
Neil

 

[Terrywookfit]

I would check / replace any ball valve diaphragms.
A pressure fluctuation can cause banging / vibration if they have hardened.

 

[GoodDIYjob]

Have you checked to see the direction of flow on the stop tap you mention. Can you get access to it?

 

[CBW]

I would check / replace any ball valve diaphragms.
A pressure fluctuation can cause banging / vibration if they have hardened.

OP said he’s had it replaced?

 

[nrestell]

Hi,
An interesting development (possibly)...

Last night I switched my combi boiler off completely all night and I didn't get any of the banging that I usually get.

Could my combi boiler be causing my banging pipes after having been on for a certain length of time?

Neil