Tank overflows on start-up

[allenfrenchy]

I just finished moving my tank (a 365 mile move, but that's another story) and set it up in the basement. When the main pump starts the built-in overflows do not always start flowinf and the pump overflowed. The tank is a 125gal All-glass reef ready with built-in corner overflows. With the new set-up I have added a 100gal sump made from a plastic stock tank. The problem is that the top of the sump is at about the same height as the bottom of the tank so the tubing which comes off the bottom of the tank dips down below the top of the sump and then has to rise back up a bit. Sometimes the flow starts just fine when the pump comes on but once the tubing got an air-lock or something and the water just backed up until it over-flowed.
Any ideas on how I can make sure the flow always starts right in case of the power going off and coming back on when I'm not around?

 

[2poor2reef]

I'm no plumbing expert but it sounds to me like you have plumbed it so that it requires maintaining a siphon to get above the rim of the sump. That means you have to attack maintaining siphon just like you would with a hang-on overflow. Ie: using a venturi air pump to draw out the air, etc. Personally, since your sump is plastic I would try to drill it and use a bulkhead to re-plumb so that no lift is required to drain the overflow. But that's just my opinion.

 

[allenfrenchy]

I think you are onto something there. Technically there is not a siphon-it could still flow with some air in the tube if there is enough forward pressure. The air block which occurs is a similar problem though in that air has to be pushed against gravity to get things going.
If I install a bulkhead just 6 in or so down from the top of the tank for the return line that should fix the problem. Thanks.