Originally Posted by Greg Wright
Tomorrow, I will turn the pump off and check the temp of the furthest valve with the yellow valve on the recirc line open and with it shut. That should confirm weather the missing check valve is the problem.
What are the advantages of using a spring check valve instead of a regular check valve?
A regular check valve uses back pressure to close it. Your pressure will be equalized once the pump is off, allowing it to fall open. A spring check will close when the pump turns off and stay closed