"Clank" in a HW boiler system.

bucksnort

My Son bought a house in VA this Summer with a WM HW boiler and HW radiators. When I visited him over Thanksgiving I noticed the radiators or something would every once in a while sound like a big tap on the system like someone hit a pipe with a hammer. What is this? Expansion, low water? Some of the rads are 8-10 feet long. He has a smallish bladder tank on the system. Would a bigger tank help?

mattmia2

Are these standing cast iron radiators or fin tube baseboard? It is something that is binding as the metal expands or contracts. The expansion tank has nothing to do with this.

bucksnort

mattmia2 said:

Are these standing cast iron radiators or fin tube baseboard? It is something that is binding as the metal expands or contracts. The expansion tank has nothing to do with this.

They're a mixture or tall iron and low and long iron rads. It sounds like someone hitting hitting a rad with a hammer. Not winding up and hitting it but more than a love tap. My house the rads will ping as they cool off sometime. It's been converted years ago from coal at one time as the house is 100 years old.

bburd

The noise is from thermal expansion and contraction, which causes the pipes and radiators to move against the other parts of the house. It may be possible to reduce this if you can find areas that are binding, like where pipes pass through flooring or around structural members, and insert something to allow the parts to move gently rather than abruptly; pieces of plastic milk jug tend to work well.

bucksnort

bburd said:

The noise is from thermal expansion and contraction, which causes the pipes and radiators to move against the other parts of the house. It may be possible to reduce this if you can find areas that are binding, like where pipes pass through flooring or around structural members, and insert something to allow the parts to move gently rather than abruptly; pieces of plastic milk jug tend to work well.

That's kinda what I was thinking. When the massive rads cool down the supply pipes are cooling down faster and rubbing on something. I noticed it most in the living room so maybe he can isolate it to pinpoint it better.