Closed Loop Question!

[racer69]

I put a cl on a 90 gal that I drilled. It has a 1" drain near the bottom, and two 3/4" returns near the top. I put a Mag24 pump on the system and it is amazingly loud (cavitation?). I do have ball valves on both return lines, but I don't want to restrict the flow that much. Is there a better size pump for this set-up and how would you calculate to determine the size?:)

[seacowboy]

this is exactly how i am doing a closed loop on my 20 gallon. a 1" inlet and 2 .75" outlets. I am planning on using a mag 5 but you could probably use a mag 7. I dont know if you could go with the mag 9 because 1" bulkheads are really only rated for 600 gph.

[racer69]

Could I add a 2" dia. pipe below the ball valve on the intake, and reduce it back to the 1"? Would this help with the cavitation? I don't feel like I am getting enough water to the mag24.

[racer69]

Any Suggestions?