Heater Plumbing Inquiry

[Airras]

Hi forum,

I will be attaching a heater to my system and will add (2) 3-way valves to the system by way of "H" set up. I was under the assumption that a check valve would be needed prior to the SWG but I am being told that if I am adding the 2 valves a check valve is unnecessary. This would support if I was only adding one 3 way valve a check valve would be needed to prevent back flow. Does the board agree?

 

[JasonLion]

There are many ways to plumb a heater bypass. It really depends on what you are trying to do.

If you are trying to bypass the heater when the heater is not in use to improve system efficiency, all you need is a simple two way valve on the bypass pipe.

If you are trying to allow the heater to be isolated so it can be serviced, then you need one three way valve and a check valve. Some people prefer to use three simple on off valves for this same setup, one on each connection to the heater and one on the bypass pipe. You can also get the same effect with two three way valves.

If you are bypassing the heater because your pump flow rates exceeds the max flow rate for the heater, the you need a spring check valve on the bypass pipe.

I can't think of any reason to have two three way valves and a check valve.