Flow Rate Discrepancy

Jrapa86 · Dec 7, 2022

When I have the COR pump running, lets say at only 5%, the tank level is fine (even though 5% seems low but doesnt make a huge difference to lets say 20%). However, when I turn on the UV sterilizer pump, the display tank overflows. What confuses me is that the flow rate on the UV sterilizer is only reading at 90gph. So I open up my two return drains fully, and the tank still overflows, and the CS102 overhead can't keep up. However, the overflow is rated to handle over 1200gph. The second problem is, why is my pump only outputting 90 gph? Researching the head, I should still be operating at a much higher rate than this. I'm baffled. Any suggestions?

I currently have an Apex COR pump with 1" PVC, 4ft of height to the tank, using 4 elbows and a check valve as well as an apex flow meter (1").
On a separate pump (CompactON 5000 (1320 GPH) - Eheim) I have running to a 8 Watt Classic UV Sterilizer. 4ft height. 4 elbows. 1 check valve. Apex Flow Meter (1").
I have an overflow: Deluxe CS102 Overflow with Lid and Air Pump - CPR Aquatics

mdb_talon · Dec 7, 2022

My assumption is the pump throughout is a lot more than 90gph. I would turn off the return pump and just use the UV pump as a test and divert to a 5g bucket if you can somehow. Time how much water you get in 60 seconds. Should be approximately 1.5g if flow meter saying 90gph and my math is forrect

blaxsun · Dec 7, 2022

I'd need some more info on your setup and how you have everything plumbed (images, details, etc.), but no - something doesn't sound right. @mdb_talon has good suggestions.