How to Calculate Overflow Capacity

[Squeaky McMurdo]

I’m thinking about adding another return pump for my 125 gallon. The one on it is a Rio of some flavor and I have another Rio 2100 that just needs a new impeller. I know some of you hate Rios. I understand, but they came with my 60 gallon that I got for free. As did my overflow box of unknown brand. Right now, water is trickling quite slowly through my sump, so I think it could handle 2x as much. The overflow box and weir are only half full as well.

How do I calculate how much it can handle?

 

[miPapareef]

Trial and error. Hopefully no flood.

Add a valve to the output of the second pump and open the valve slowly until your drain can’t keep up. Then you’ll know the max it can handle. Hopefully more than the max the pump can deliver.

There are online flow calculators for weirs and pipes but way too many assumptions needed to be anything more than directional info.