Return Pump Size?


New member
I am putting a sump in and need a pump size for a single overflow. What size pump is usually used?



New member
If its a single 1" drain u can estimate around 600GPH give or take.

If you have a 40 gallon tank you dont want to use a return pump that will come anywhere close to 600GPH.

Most people will agree that you want slow flow through your sump, 5-10x the size of your tank, 40Gallon*4=200GPH

There is a headloss calculator on the main page on the left. Depending on how many bends, or how far you go, this will reduce your GPH.

If you want a top notch pump look at the Eheim 1250. Should be just around right for your setup.

The biggest problem you get with going faster like a Mag 5 or 7 is you'll have water moving so fast u'll get tons of micro bubbles.. amoung other issues. Also if you start to come close to your overflows limit you'll hear a big waterfall effect...


Premium Member
Remember you can always "T" on the return side of the pump and send some water back to the sump itself - that way you can control the flow rate at the tank even if the pump is a little big.

Just a thought.



Reef Ninja
Premium Member
I was planning on putting a T on the return side of the pump to control the flow. That should let you control the flow to the main tank.


New member
Depending on your height, a mag 7 would be a great return pump. Your overflow should not have a problem handling the flow.