my dad and i were working on a wet/dry filter. something came up about "what if the suction fails, and the tank overflows from the water being pumped back up." he said if it overflowed, i would have to tear down my tanks! in the overflow, i have slits rangin from this size: - to this size: --- . the tube coming out of the tank is PVC, which attaches to clear hose then into a valve system, ending up in the wet/dry. i have fairly fine mesh on the end of the intake tube, so if anything DID get in, it couldnt go down and clog the tube. IS THERE ANY RISK!?!

Don't use a siphon overflow. Drill the tank and allow it to naturally flow to the sump. Then make sure there's just enough water to operate, but not enough that it overflows. That way there's no siphon to break. If the power goes out, the pump stops. After a few seconds, the water level goes down enough in the main tank that it won't pass through the pre-filter. Definitely the way I am going. Sergeant Major has a great plan for putting the sump above your tank. He claims it's fool proof as well. I'd wait a bit and let him comment. You might like his idea better.

Well my idea is essentially the same, except that you drill the sump instead of the main tank, then put it above the tank (preferrably in a cabinet). The biggest advantage is that when the power fails on this system, the sump stays at the same level, whereas with Mazza's idea, if the main tank is overly full, and it's say a 90g tank, if the power fails it will overflow a 10g sump just to drop the level of the main tank to an inch to the bottom of the overflow. That's really about it.