plumbing noise

I have noise in my copper pipes when hot water is run through them. It sounds like an old steam radiator banging but not quite as loud. I know that it is not water hammer. Can anyone tell me what is causing this and better, if anything can be done to stop it? Thanks.
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"James Laws"
As the copper expands, it rubs against a joist or stud or maybe a heating duct. It can be difficult to pin down. You can start to listen around to narrow it down. If it doesn't bother you too much, just live with it.
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Is it the same principle thqat would apply to copper pipe hot water baseboard heat?......cuz i'm in a rental unit, 3 floors, boiler in lowest level,master on the third level.....and this system "talks" aplenty....had that zone drained once and refilled to rid of any air in the line, and the "clanking" is still there....do you think this is also a joist rub?.....bob

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"bosumo"
Yes. The thing is that I find these sounds to be soothing and part of a house's personality. I wouldn't expect it in a brand new construction, but over time, wood swells and sags. I like the noises my home makes!
However, when you completely drain a hydronic heating system, the new water always has air dissolved in it. Usually the automatic air eliminators do the trick, but sometimes it must be bled from the highest points in each zone. Air doesn't make "clanking." It usually sounds more like water running.
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Mike, thanks for the reply. So when i construct my new home with hot water baseboard, i need to make sure that every penetration through wood needs to be wrapped in that black foam pipe insulation?.....also, there seems to be a trend toward plastic piping, "pex" i think i recall reading....is that ever used for the runs to the fin assembly?.....thanks....bob

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my guess is that it may be at the water heater itself......some of the new water heaters have a constrictive device in the outlet......remove it and no more sound........

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