[Canadian]

Originally Posted by StirCrazy

I am going to side with sphelps on this one, a single overflow will be more efficient, but in the design above it won't. for a single overflow to outperform two it has to be larger, this is why the coast to coast works so good. I would recommend going with one large one in the middle, maybe 24" wide by 3" deep. or how ever deep enough you need to get your bulkheads in. If you can go even wider.

Also we shoot ourselves in the foot when we make overflows because we put teeth in them. this allows water flow from below the surface to enter the overflow.

My last tank I think I did about 5 different overflow designs over the years and the one I was most happy with was an acrylic overflow box with no teeth, just a smoothed out rounded edge. this combined with a large linear distance will cause a very thin film of water to flow over the edge. I think in my 94 I had 1500gph overflowing at a water thickness of less than 1 mm.

Steve

I don't know what part of sphelp's points you agree with Steve when you say:

for a single overflow to outperform two it has to be larger, this is why the coast to coast works so good

because sphelps is contending that a larger overflow would decrease the suction of the overflow and make it less efficient.