power outage

I was thinking of using a overflow box, to sump, through skimmer, to return pump, my question if the power goes out I figure once the ov box drew enough water out of tank it would lose vacum (I don't think I spelled that right) and stop, now when power comes back on the pump in sump would come back on but overflow would not start so pump would run dry and burn up, right? I'm sure there is something for this I've just never heard of what backups or solutions are available. Could someone enlighten me please.

 

No when the sump pump starts up it will put pressure on the overflow and restarting the circulation. You should not loose the siphon if the overflow is set up right. The water will backflow into the sump lowering the DT level below the overflow's spill area.

 

The overflow works on a siphon, as long as its properly setup it wont loose the siphon when the power fails. the only siphon you want to break is the one caused by the return line, created when the pump shut off and the flow direction reversed. This can easily be done by drilling two 1/8" holes in the return line about 1/2" under the waterline, this way the suction is broken when the water level falls low enough to start drawing air thru the holes.
Now, the payoff is when the power is restored the tank will fill and as it enters into the overflow box the siphon will restore preventing the sump from running dry

edit: lol, 2in10 has a much simpler way of stating it

 

I was thinking the overflow would drain completely into sump, breaking vacuum at the aquarium.

 

not if it's properly setup

 

the whole point of an overflow box instead of just a tube is to prevent this.