Starting siphon after power failure


New member
I am currently leak testing my plumbing and testing for problems...of course I found one. I have two 1" bulkheads in my overflow that have down turned elbows. When I turn the pump on after simulating a power failure (by unplugging all the pumps) my closed loop starts up fine but the return pump in my sump just empties out the compartment and the siphon from my overflow does not really start.

To be slightly more descriptive, the elbows are completely submerged but they don't get a good siphon going and don't supply enough water to the sump for the return pump. I do have a ball valve to control how much water flows to the sump, so I don't overwhelm the return pump. If I open it up all the water, some air is purged, then I can throttle it back some and everything works fine...until I cut power again. If I remove the down turned elbows from inside the overflow it also starts up fine, but then it sucks some air which in itself is not noisy, but it is kind of noisy in the sump when they bubble up.

So my questions is, is there anything simply I can do to fix this? I did not put any Durso style tubes in the back, the bulkheads go straight to 90 elbows and into the sump. I have a feeling if I replace the elbow with a tee and put a cap with a hole in it on the top portion it may fix the problem...but I am not sure, plus this would require buying quite a few parts since it is glued up already.

Sorry about the long post.


I do have a ball valve to control how much water flows to the sump, so I don't overwhelm the return pump.
I think you are having the opposite problem. What pump are you using for the return? My thought is that when the sump fills after the power is cut, the pump is filling the tank slightly faster than the return can handle. I would put the ball valve above the pump and throttle the pump back slightly. You could also put a T and divert some of the return back into the sump. I would have the returns free flow into the sump. I hope I explained this clearly. Maybe you could post a pic of your setup? Here is how I have mine setup:


The T above the pump diverts some water back into the sump and there is a ball valve at the top of the picture. My pump is probably pushing 550 GPH and the return is rated at 700 GPH.