Overflow size and return pump

Eng Keat

New member
Hi Grey,

Really enjoyed all the three articles on the sump (hope more is coming:) )

Anyway one question, how do I calculate how powerful a return pump do I need to put in the sump to pump the water back to the main tank?

example - Pump putting back water at a faster rate than overflow -> empty water in sump ????

I guess the other way round (pump returning water at a slower rate than overflow) should not be a problem.

Eng Keat
You are kind of working from the end trying to get to the beginning. It's much easier to start at what kind of flow you want to achieve.

Typically, the first step is to determine the flow that you will need to put through your sump. Then be sure that all the other pieces of the system can handle that flow.

If all the water circulation in your tank is being accomplished by your return pump, then the circulation needs of your tank will determine the flow through the sump. If you are running a closed loop, or some other means of circulation in your tank, then the flow through your sump is only determined by the need to move enough water through it to keep the heaters / skimmers / etc, working efficiently.

One you've determined what kind of flow you want through your sump, then you can work on how to get your drain plumbing to get it back to the sump (large enough drain holes, etc) quickly enough using the drain calculator. If the drain calculator is telling you that you should have a 2" drain and you only have a 1" drain, then you know you have a problem. If it's close, then you'll be able to work through the issues pretty easily.

I know I haven't given you a complete answer, but I don't have a simple answer. You've certainly given me plenty of food for thought on subject matter for the future. ;)

The following sentence will probably be of more help than the entire rest of the post. Remember that if you buy a pump that's too big for your plumbing to handle, you can always throttle it back, but if you buy a pump that's too small you can't make it pump more water.

I hope that helped a little.
Hey man, thanks a lot for your reply. It definitly does help and I had to relook at my plan from another view.

Eng Keat