How to determine overflow GPH?

[minibowmatt]

I want to build an internal Acrylic Overflow. I know i want teeth on my overflow to prevent snails etc. from getting in, but how do I figure out how large to make the box and the teeth?

 

[JesseCNC]

Matt,

This is just a rough guideline, but figure 9 linear inches for every 600GPH of flow. The 9 linear inches can be 3x3x3, 2x5x2, etc.

Jesse

 

[Anonymous]

For the overflow box I am building for my 150 gal, it's edge is about 44 inches long total, and I cut a teeth every inch interval for a length of two inches using a 3/4 inch router bit. It should be able to handle 2000 GPH, but I did not test it yet.

There is no issue for the overflow box since if the pump is too fast, the water just spill over higher. You can make shorter cut, and if you want it to go faster, you can increase the cut height using a dremel tool, etc.... My point is that it is not that critical, just build your box as big as you can, without taking too much space, but still big enough to work around (install bulkhead, etc.) after it is glued. The important thing is the size of the bulkhead.