determining flow rate?

[burntricer]

hey r/s, whats up? anyway if you've been following along with my tank atall, ive had a few designs for a sump, and now ive got one i wanna go with. I know im going to be using an overflow to feed the fuge/sump, but what i dont know is how big of a pump to get to match the flow of the overflow, to the flow of the pump.

any help s greatly appreciated!!

[Clownfish518]

I personally prefer a low flow rate through the sump, and don't depend on the return to do a lot of the in tank circulation. I always run my return pump lower than my flow rate for the overflow. My overflow right now is rated at 1500 GPH on my 90, and my return pump is between 600-700 GPH.

Part of the difference is I have a dual overflow, so that if a snail clogs up one side I don't have any problems, so I am running 600-700 GPH out of a possible 750 GPH

[DaveK]

You can figure a typical overflow on a reef ready system can handle about 600 - 900 gph. If you have a large tank with two overflows you can double that number.

I would recommend the setup Clownfish518 recommends. Keep the return pump slightly on the low side.

If you need additional circulation, add powerheads or other pumps for circulation.

[burntricer]

i was planning on doing a low flow setup, what i dont know, is how you go about determining that the same amount of water is leaving the sump as is coming into it.

[Clownfish518]

As long as overflow is sized for more flow than the return pump, then the water entering the sump equals the water leaving it. Simple displacement. I guess I don't understand the question.

[burntricer]

i get that part

k ill re phrase it

im DIY'ing my overflow box. i have to buy a pump rated at X GpH.

i need to know how to calculate the size of the pump i need to match my over flow. how do i do that.

[Eric]

Well without knowing the details of the overflow there is not much we can offer.

Is it an internal,external, or hang on overflow? Also what size are the drains in the overflow? If the tank Is drilled, where in the back or bottom?

There are calculators online to help you decide as well. If you are using a 1" Id bulkhead the flow rate is 600-900gph depending on the stand pipe and setup. There can be a lot of variation in the flow rate.

There are a few factors we need to know before we can help. Please give as much detail as possible on you set up.

Thanks
Eric

[Clownfish518]

Mike Kirkman and Scott Vallembois wrote an article last year in FAMA doing flow tests. They tested flow rates with all sorts of conditions. Here is what they found:

2 inch bulkhead will flow approximately 1350 GPH
1 1/2 inch bulkhead will flow approximately 975 GPH
1 inch bulkhead will flow approximately 350 GPH
3/4 inch bulkhead will flow approximately 165 GPH

Here is the link to their test results. You can get more flow through a pipe, but only by starting a siphon.

Aquarium Bulkhead Tests

[Eric]

Yeah without a stand pipe bulkhead flow is slowed dramatically and without a stand pipe they are also very noisy.