[Funky_Fish14]

I definitely agree with Shrimpchip's first point, that water flow really should have a system separate from just the return.

Responding to you, Shrimpchips:

Im not sure what 24" you are talking about? The 'region' of water that produces the backflow would be the part between the pump and the high point. (Same as in any system). It would take only a small amount of air in at the top of the upper loop to break the syphon. Infact it depends mostly on placement of the hole where the air comes in and the size/length of that upper loop. If there is a large section horizontally oriented in the top of that loop, then I could see a problem, but with a small upper point to the loop (by loop I mean an upside down U, in whichever shape is the most convinient for the situation), the air would be drawn in and break the syphon quickly (assuming the air-hole is large enough, which should obviously be tested).

I am absolutely certain that this could be done with less than 1gallon of water (from the back-syphon) draining back into the sump even with two return lines in such a way. (ofcourse with the anti-syphon holes, the part between that and the pump will entirely drain, but I mean less than 1 gallon to break the syphon, the rest of the water quantity depends on the amount of plumbing/size).

+ Setting this up correctly, there is no way any part (anti-syphon hole) sould become clogged. And confirming that (on any system) is simply part of regular maintenance.

Cheers,

Chris