noise pipe hydronic radiant heat

Frankmiester

I have a friend who has a pipe that travels through the lower part of the floor to the upper floor and when the heat turns on the pipe starts to make a horrible banging noise. After doing some research I found pipes can expand considerably in length and there might not be enough room for the new expansion from the new heating system that was just installed. They went from a traditional oil burner to a tankless gas heat.

Any suggestions on a fix?

I had ideas of cutting a small section of pipe out to replace with pex and see if this takes up the expansion by softening the expansion in the length of the pipe. possibly stopping this issue.

Jamie Hall

Oh dear. No, a short section of PEX isn't going to help, unless you could arrange a large — say three foot diameter — in the middle of the line somewhere, and suspend the cut ends of the existing pipe so they can expand and contract freely. The chances are that the old system ran quite happily at a more or less constant temperature, so expansion wasn't an issue. The new one, with a tankless heater doesn't — it's either on or very much off.

Examine the piping carefully. It is remotely possible that you can rearrange the way the piping is supported and touches various bits of the house so that there is room for expansion for the rapid and large temperature swings from the new tankless unit. Most likely not, but worth looking at.

You may be able to cure the problem by rearranging the near boiler piping so that you have more or less constant temperature circulation — hotter on cold days, cooler on warmer ones, but running all the time — with the boiler adding heat to the loop when needed. This will require a mixing valve — controlled preferably by outdoor reset — and another pump.

Depending on the tankless (what make and model is it?) you may also have to add a buffer tank to the system, so that it doesn't turn on and off too often.