Overflowing help...

[sj022698]

Please look at my photo
My tank is tempered so I can't drill.
If it blows a circuit breaker it wouldn't come back on unless I flipped it, right? However a power outage in which the power just kicks off and comes back on would be more of a problem, correct?
I don't even have the water in my tank yet so I'm pretty unfamiliar with how that would all work. If that water siphons out, wouldn't it stop once it got below the overflow box since it has a U-Tube? I have about 5 gallons of empty space in my sump so wouldn't it just siphon into that and not overflow anything?
I'm just worried somehow my whole tank would drain or a mass amount of water on the floor while I'm out of town or at work.
I read this article. Should I buy this peice???
"How do you prevent the sump from overflowing in a power outage ??
As I stated above, Only the water in the tank that rises above the lip of the overflow box can flow down to the sump. It is impossible for the overflow box to ever drop the water level any lower than the lip of the overflow box. So, even with the power off, the water level in the tank will drop until the water level is just barely below the lip of the overflow box. You need to set up your sump and overflow box so that the sump can always hold that much water. In my 29g sump with the pump off, the sump should contain about 20 gallons of water. When the pump is running, the level in the main tank rises, and the level in the sump is around 10 gallons.
While it's true that the overflow box won't cause the sump to overflow, there is one situation that could if you don't take precautions. In a planted tank, we almost always want the pump-return output to be below the tank water level. Otherwise it creates a lot of surface agitation and releases any injected CO2. But with the end of the pump return hose below the water surface, if the pump is shut off, water will flow back down the return hose thru the pump and into the sump. Water will flow backwards until the tank level drops below the end of the return hose. If the return hose ends just below the water surface, then very little water will flow backwards. But, if your pump return output was at the very bottom of the tank, then ALL of your tank would drain backwards thru the pump. BIG FLOOD!.
You have a couple options to prevent this flood. Easiest/cheapest is just to position the pump return output just below the normal "pump on" water level. If you don't mind spending a few bucks, you can buy a check-valve that will allow water to flow from the pump to the tank, but block any backwards flow from the tank to the pump. They are available from www.DrsFosterSmith.com and www.ThatPetPlace.com

[golfish]

I'd go a little bigger then a pin hole. I drill more like a 1/4" hole right at or just above the water line. This will stop the back siphon.

You can do the check valve thing but you'll want to back it up with the drilled hole (siphon break) Check valve are known to fail if not kept clean, even then they can fail.