DE Coming Through Main Drain

[DanF]

One last question again: Where would the best location for the check valve be? Options I see are on the vertical pipe coming up from pump, or the horizontal pipe between pump and filter.

 

[JamesW]

One last question again: Where would the best location for the check valve be? Options I see are on the vertical pipe coming up from pump, or the horizontal pipe between pump and filter.

Vertical is more reliable, but either spot will work.