noisy knocking noise

[ianmulluk]

Does anyone know what would cause an annoying "tapping" noise in one of our radiators upstairs.
I have shut the water supply off to the radiator but within half an hour of the heating coming on this sort of tapping , knocking noise starts.
Not that loud but very annoying.
Is it something to do with the pipes expanding under the heat ??
Is our water temp too high??

Not sure - any help would be great

ian

 

[hj]

tap tap

No way of telling without hearing the sound and checking where it is coming from. Do you have hot water or steam heat?