Knocking sound from radiant heat


Old 11-17-08, 01:54 PM
Thread Starter
Join Date: Nov 2008
Location: Pennsylvania
Posts: 1
Knocking sound from radiant heat

I have hot water radiant heat installed under my first-level floor. It works fine, but I get a knocking sound from one end of my bedroom when the programmable thermostat turns on the system in the morning. I'm familiar with baseboard radiant systems clicking and pinging as they are heated and cool off, and I'm sure it's a similar expansion and contraction situation. But the knocking wakes me up before I'm ready to wake up. I have plastic tubing installed underneath the wood subfloor. Is there some type of lubricant I can apply where the tubing is held up under the subfloor? Is there an alternate way to attache the tubing to eliminate the knocking sound? Help!!
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Old 11-17-08, 09:59 PM
Join Date: Nov 2008
Posts: 1
We have a very similar problem with our in-floor radiant heat system. When it kicks on we get a series of loud knocking noises. Unfortunately, I haven't been able to find someone to provide a solution, so I'm anxious to see if you have any luck here.
Old 11-18-08, 07:13 AM
Join Date: Nov 2004
Location: USA
Posts: 1,959
I once lived in a home with a boiler system hot water baseboard heat.I was told these sounds,which are common to these systems,are the sounds of the pipes and/or metal components expanding as the heated water passes through them and they heat up.I was told that this was normal and in the years I lived with it there was never a problem.
Old 11-18-08, 07:40 AM
Join Date: Oct 2008
Location: New England
Posts: 9,999
Hi, I recently worked on a home with radiant floor heat and a section was open where we could see it from the basement. His pex was snapped into a u-channel mounted to the floor above and had similar problems with the tubing expanding and contracting and making noise. The heating contractor came back and installed teflon tape in all of the u-channel and snapped the pex back in. No more noise.

Not sure if this is related to your situations but it might.


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