Originally Posted by barchtruong
don't mean to steal ur post,
I was always wondering about the overflow boxes.
What would happen if you have a power outage,
the return pump is off and the over flow box keeps filling the sump up,
that would be a disaster to find out after a work day that the tank is empty and the carpet floor are filled up with salt water.
youroverflow box is set at a level that if power goes out it will only take
the amout of water in your tank you set it at .which is also the amount that
your sump can handle.and a check valve prevents backflow on the output
side .imo, no more risky than a canister hose faulting the typical canister
input is way down in the tank .that could practicaly take all water out not to knock canisters ,i have one on a 55g.if your really curious some
people have good diagrams on how they function.