new coast to coast overflow height?


New member
I have just removed my old corner overflow and am measuring things out for my new BA system. I installed my old corner overflow right at the bottom of the plastic trim. I always wished I had moved it down lower as the water ran too high.

I understand that the c2c will take a smaller slice of water off the top. Where should I mount the top of the overflow? I am thinking right on the bottom of the trim again, but I hate to make the same mistake twice!

Flat overflow( no teeth) on a standard 4' 120 Gal.

Thanks a ton.


New member
Top of the overflow should be even with the bottom of the trim on the outside of the tank. E.G. 1" below the top edge of the glass. The water level in the overflow should be 1" below the top edge of the weir. This gives a 2.5" margin for water level rise, before flooding, which is more than enough. The dry emergency should be running before the water level reaches the top of the weir, but that can vary a small amount. Much higher than that, the open channel should kick in as well.