Noisy central heating radiators.

[Why??]

We had brand new central heating put in just over a year ago and one or two of the radiators make tapping noises when warming up/cooling down. I know that the pipes will expand/contract and this could be the cause.

I did get the company back out to look at it and they said it could also be that if the floor board has been cut a bit too snuggly where the pipes touch it that may be causing the noise, and I could try wedging something like a small piece of foam between the board and the pipe.

My main questions are-

How come it only happens on one/two radiators and not the others?

Is there anything I can do to stop it?

Can anyone help?

[Robert G]

I think the company were correct. It's the pipes not the radiators. Whether the places where it occurs are easily accessible remains for you to ascertain. Hopefully it's where the pipe passes through the floor boards, but it could be where it passes through the floor beams beneath. If you cannot enlarge the hole through which the pipe passes, you could try to pack a little grease in around the pipe.

[RAYMAN]

If it is the rads the only thing I can think of is the only friction area is where the rad sits on the wall-bracket you need to somehow cushion that area.