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Rogergolf66 05-05-2007 06:38 AM

I just bought a 125 not predrilled. I wanted to know how can I figure out the amount of water flow an overflow will handel. in other words how big of a pump I can get for it.


Rogergolf66 05-05-2007 06:40 AM

water cycles
I am putting up a new tank 125 72 inches long.

I was wondering please more then one person answer this question because I know that there is more then one aswer. How many times should the water cycle from the main tank the the sump/refugium in an hour?


jones57742 05-05-2007 07:45 AM

Don't know anything about salt water.

Q is the overflow in Cubic Feet per Second (CFS)
H is the dimension from the top of the overflow (the weir) to the water surface in Feet
L is the length of the overflow in Feet.
1 CFS = 448.83 gpm

This is general weir equation with the coefficient (2.67) being conservative.


Overlow height (H) = 0.5 Inches
Weir Length (L) = 2 Feet

Q= 4.58 * 2 * (0.5/12)^1.5
Q=0.077907382 CFS
Q= 35 gpm

At H= 1.0 Inches
Q= 99 gpm


caferacermike 05-05-2007 09:32 AM

What Jones is saying is that the overflow is dictated by the pump size. An overflow can only remove what is put back into the tank, no more than that. So if you have a pump that can handle 400gph but an overflow that could handle 600gph your overflow CANNOT suck more water out than the pump can put back in. It's simple, the weir sit 1/8th-1/4" above the water line, if more water overflowed the water line would then be below the weir and could not overflow. Generally a 1" connection in the back of the overflow box is rated for 600gph. 2 Utubes or 2x 1" bulkheads= 1,200GPH. The cycle time of a sump should be between 5-10 times per hour. At that you'd be looking for 625gph-1,250. I'd get an Eheim 1262 that should be around 900GPH at the actual return point. You could go a little larger than that but may need to restrict the output of the pump with a ball valve. What you are interested in with the sump is "contact time". If the water moves to quickly through the sump/fuge the equipment will not strip the water clean.

Rogergolf66 05-05-2007 03:32 PM

great info thank...

Well I want the water through the refugium to move throw slow. I could use a sump with the filter pad in it, and use a seperate pump to feed the refugium? how would that be done?


Rogergolf66 05-05-2007 03:39 PM

thanks. any inline recomendations for pump. That would help keep the temp down.


caferacermike 05-07-2007 05:15 PM

Eheim pumps run the coolest since they use the least amount of electricity. Instead of adding another pump think about teeing from the return or suction line to the fuge. Add a ball valve to slow the water headed towards the fuge to what you'd like it to be. I added a tee and a valve headed towards my fuge from my return line. It was very easy to do.

Rogergolf66 05-07-2007 08:57 PM

that sounds great so my sump and refug are differnt? also is there another over flow on the refug to the sump? How do I get the water back the tank this way?

Rogergolf66 05-07-2007 10:25 PM

is this the pump you were talking about?

Rogergolf66 05-08-2007 06:57 PM

Well I must not be as good at math as I thought. Can someone please tell me how much water this over flow will handle?

Also how close should I push the limit with an over flow. I mean if it handles 1,200 gallons should I do 1,200 gallon pump or should I do 950 gallons to be safe?

Double Bulkhead overflow filter box.
The dimensions

8.5"L x 10.5"W x 12"H
1inch tubes

Thank You so much for your help.


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