Central Heating Pipes

[ducey99]

When my central heating is turned on the pipes make a 'banging' noise. What could cause this?

[NORMANTHEDOG]

air in the system,get it bled by a plumber

[ducey99]

I've bled the system but it's still doing it. Could it be the pipes banging against the joists.

[leighb]

Hi, sounds like the system needs a clean, Get a cleaner from a good diy store and put it in the header tank, if its a combi system, put it in a radiator and repressurise, Hope this helps

[buildersmate]

It probably isn't what the above postings suggest. The key is that you say it does it when the heating comes on. It is caused by what you suggested yourself - the pipes banging against the joists. As the water heats up the copper expands (it will only happen with copper - not plastic) and the pipes move slightly. Where they are too tight through a slot cut in the joist or noggin, they move in a series of 'jumps' that sound like bangs. I'm afraid it is very difficult to stop it.

[Hard@it]

You possibly have thermostatic valves on the return instead of the flow in some instances. When you hear the banging go round one at a time and turn them off, you will also feel vibration at the valve. At least you will know if it's not the valves. Hard@it

[taff1949]

if its oil fired ,the water is static in the pipes when off. on startup the pump kicks in to assist water circulation therefore creating a momentary surge, any pipes not properly affixed especially long ones will vibrate on joists and other fixings, hope this helps

[rabseenesbit]

Ithink hard@it got the correct answer.I had my thermo valves on the wrong side of the radiator,got them changed and i haven,t had a problem since