Using swing check valve for downward flow?

[don_chuwish]

I know it doesn't seem to make sense installing a check valve in a downward flow situation, but my CPR HOB Refugium with skimmer dumps a lot of water back into the DT whenever the pump is off.
The only place in the intake plumbing I can see to install a check valve is on the skimmer side, where the flow is down toward the bottom of the chamber.
Would the flap close properly as soon as flow started to reverse?

Thanks!

- D