Aqualifter question

[Delphinus]

It doesn't have a mechanism to stop flow when it's off. If both tubes are under the water line and you get a continuous slug of water from one end to the other then when the pump is off, water is going to siphon from the higher water level to the lower (ie., either forward or backwards) regardless of where the pump itself is situated. You should have your output tube in the air higher than the source water and dripping into the sump. That way when the pump is off, the water in the lines falls back into the FW reservoir, the lines fill with air and the siphon breaks. It means it has to reprime each time but I think the Aqualifter can handle self-priming. If not, then you could try a check valve.

HTH!