Solar Panel return check valve?

[LKB]

Hi All,
Getting ready to do a solar system, Pentair easy touch upgrade and Pentail Intelliflo XF pump.

The solar plumbing diagrams I have seen show;
from filter –check valve- “T” to bypass and 3 way valve
3 way valve to solar feed and solar return “T”
Bypass to solar return-heater supply “T”
This includes isolation valves BTW

My question is shouldn’t there be a second check valve on the Solar return before the flow hits the first “T” (in flow direction), to keep water from flowing up into the return when the valve is off?
The diagrams that do not use the bypass show the check valve in this location, so what am I missing?

Thanks,
LB

 

[JasonLion]

Ideally, yes there should be another check valve. But it is not required. The check valve prevents water from running backwards up the return pipe when the solar panels are off. However there isn't very much harm in allowing that, just some small loss of panel lifetime.