Originally Posted by huma-huma
See my dilema is that i can technically fill the tank high enough to get both overflows running, but my temp return pump isnt strong enough to supply 2 overflows
then it makes this method work for you. by having a pump that returns slower than you can drain is great and preferred . so long as the drain that does not have the valve is above your full siphon line but below where your tank will overflow for safety should a snail or something further block the flow through your main drain.