Loud bangs when system cools - PLEASE help!

Have a pumped system, which generally seems to be working fine.

However, during the night we get several bangs, which seem to come from the system somewhere (but not the boiler area). Sometimes these are very loud. Each time the noise can be best described as a \\\'thump-thump\\\'. Often wakes us up.

These can occur several hours after the system has been switched off. It\\\'s very strange and is really doing our head in, any suggestions people might have would be appreciated more than you know.

(Interestingly - or not - it seem that my father-in-law has a similar problem).

perhaps you have a micro leak on ch system. (do rad pipes dissapear into concrete .) and the f/e tank is topping up. some do make a loud noise .pipes vibrating.

so tie up ballcock one night ...and see wot appens.

Thanks. I'll check on the pipes (we've only been there 6 months). meanwhile, I'll try that with the ballcock.

Any other suggestions?

I was thinking pipes contracting as they cool. If they are not free to slide easily they might be sticking against a joist or wall and snapping back abruptly.

If you lift a few floorboards you may be able to trace potential sticking points. Ease the hole or notch slightly wider and wrap the pipe in felt so it can slide freely. If you have any heating pipes under the ground floor, insulate then with the thick foam sleeves (it is useful, but not essential, to insulate pipes within the rest of the house as they can be considered to add to the heating of the house).

Radiators can also be noisy as they expand and contract. New ones are now supplied with U-shaped sliders to go between the fixing strap on the back of the rad and the wall brackets. I don't know if it is possible to buy these separately somewhere

If it makes banging or clicking noises as it cools, you should also hear similar noises as it heats up. Easier to trace under floors. ,etc.. because you know when the noise will happen.

It could well be pipes 'sticking' against a joist. I know that in places there are also 2 pipes which run alongside one another, touching.
It does make a lot of creaking sounds when it hots up (in fact quite a lot of the time).

I think I'll investigate further under the floorboards at the weekend and felt and insulate the pipes where I can. It's a job worth doing, I guess, even if it isn't the problem.

All help appreciated with this. Thanks.

Send your wife along to the DIY shed and tell her to say "Can I get felt here?"

There's no point!

She can get felt here!

My system creaked like hell, especially after it was switched from a tank fed back boiler to a pressurised combi boiler.
To solve the problem I lifted all the floorboards and under notched all the pipes then wrapped cut up old tea towels around the pipes were they touched one another and where they touched any of the building fabric. The worst place for creaking was at a set of F and R manifolds where all the 8mm pipes were squashed against the floorboard (i routed the floorboard out, under notched, repiped some of the 8mm pipes and wrapped them all with OXO tea towels).

ever since it has been soundless (apart from normal operating noises from the 105e in the loft above the bedroom!).

It was relativly easier for me to do the above as all the boards were lifted previously and there were no carpets in the property. It may help if you turn your heating\boiler stat down a tad and if you can slow the pump down, if its on setting 3 then stick it on 2, though this is generally only going to help continual flow noise and not expansion and contraction noises.