Sump turnover rate on large tanks?

[DangerDave]

1-3x turn over. Additionally, make sure it’s a proper sized sump. You want some dwell time for the water in the sump...

 

[WVNed]

I have a system were I can catch all the flow in a bucket and calculate it out. I have dual returns each with it's own pump The pumps are rated 2100gph each. I get 900 gal/hr measured from one section of my sump to the other. I suspect most people are being extremely optimistic when they talk about their flow through the sump. I have about 2.5x and it works fine.