Heater Pipe COLLAPSED!

[learthur]

Attached is a photo of the collapsed outflow pipe from my heater.
Not sure why this happened. The thermostat seems to be working fine and the pipe is only slightly warm on the outside to the touch.

Needless to say this has diminished my GPM. Dropped it from about 85 to 70.

Anyone with heater experience have any ideas, comments. The pipe is PVC SCH 40, not CPVC which I understand is what should be here.

Unless I can find some problem with the heater, I plan to simply replace the 3 ft section of pipe with CPVC.

Lee

 

[JasonLion]

This happens when the heater and pump turn off at the same time. The water stops flowing through the heater and the water that remains in the heater gets very very hot. If that extremely hot water is drawn into normal PVC pipe it will melt the pipe, which is what happened here.

There are two solutions. The first, and preferred solution, is to use a fireman switch to turn the heater off several minutes before the pump turns off. That way the heater has some time to cool down before the water stops flowing. An alternative solution, not as good but often sufficient, is to replace the pipe with CPVC, which is more heat resistant.