What size slot overflow?

[Phantom Phish]

I'm trying to design a new tank, in which I want about 3000 gallons per hour going to the sump and skimmer.

According to the overflow calculator on RC, I need almost 45 linear inches of overflow to get 3000 gph through there. I assume that means the standard overflow with teeth.

Has anyone seen a calculator, or does anyone know a formula that can calculate the flow rate through a "slot" overflow, i.e. a toothless overflow that's essentially just a slot cut in the back glass?

[Geoff]

what sized tank? have you thought of using a CLS?

my WAG is prolly cut the distance in half.

G~

[Phantom Phish]

The tank will be in the neighborhood of 300 gallons, BB and sps dominated. I'm aiming to get roughly 10x turnover going to the sump and skimmer, and then there will be a closed loop system in addition to that.

I don't understand "WAG". What is that?

[Geoff]

Originally Posted by Phantom Phish

I don't understand "WAG". What is that?

Wild @$$ Guess.

G~

[Phantom Phish]

Originally Posted by Geoff

Wild @$$ Guess.

G~

LOL. Ok, that was my "WAG" also.

[Phantom Phish]

Ok, I've been giving this a little more thought.

The RC overflow calculator recommends a minimum drain size of 2.26" diameter pipe to get 3000 gph. I assume that means one pipe with an internal diameter of 2.26". (if this assumption's wrong then I'm in trouble).

Using pi r squared for the area of a circle, that works out to a cross sectional area of about 4 square inches (3.14 x 1.13 x 1.13 = 4.009) for a pipe 2.26" diameter.

So, I figure I should be OK as long as the area of the overflow cut out is greater than the the cross sectional area of the minimum drain pipe, right?

I'm thinking that doubling that minimum to 8 square inches, and rounding up to 10 should give me a good margin for error and insure that the pipe diameter is the limiting factor to the amount of flow going to the sump, and not the overflow opening size. Does that make sense?

If thats correct, then theoretically a slot of 10 inches long and 1 inch high should do the trick.

[Geoff]

i think your thinking is correct. the problem is getting 1" of water over the overflow. generally it is only a 1/4". you would need a monster sump to handle that amount of water when the pump stops, lets say for a power outage.

G~

[Phantom Phish]

Yeah, that's a good point. To get the same area at a height of 1/4", I'd need a 40" slot, and I'm back to where I started from. ****.