Heater Making Knocking/Tapping/Clicking sort of noise

sevver

Well-known member
Mar 27, 2007
477
Morris, IL
Why would my heater make this sort of noise? The first year it didn't, but last year and now this year it has. It only does it when it is actually heating though. To me, it sounds like expansion contraction issues. Sort of like an engine cooling down. Only this is different. I need to pull the cover off of it and fire it up to see if anything is visibly making the noise though.
 

Denali

Well-known member
May 1, 2008
70
Scale formation inside the heat exchanger is one possible source for that type of noise.

Are you able to tell what part of the heater the noise is coming from? If it is coming from near the header (where the pipes go into the heater) then it might be a problem with the auto bypass.

What type of heater is it?
 

Denali

Well-known member
May 1, 2008
70
Is the heater working normally for you? By that I mean is it heating the water.
If you put your hand at a return line when the heater is running, is the water warm? hot? same as pool water?
 

Denali

Well-known member
May 1, 2008
70
sevver said:
Yes, it is working normally, it heats the water without any problems.
If you had a problem you would normally see a slowing of heating. If the heater bypass is scaled up or broken, you will get that clicking noise. The bypass is mechanical and is supposed to open in relation to the water flow to allow the right amount of water to pass through the heat exchanger.

If you look at a diagram of your heater you'll see the bypass is basically a spring with a disc attached. If it keeps up and it concerns you, I would open up the bypass and inspect the spring and disc (with system turned off). You just want to see if you can push the disc in and that the spring will close it.