closed loop help

[mission man]

I just put together a closed loop system and I believe the pump is cavitating. The pump is humming loud, and lots of bubbles coming out of the returns. I somewhat used Melevs site for an idea. I have a MAG 9.5 for the pump . I only have some 1 inch pipe on the input. Im thinking this may be the causeing the cavitation. I tried to close the ball valve on the output side a little but it didnt seem to help. Do I just need to put in a bigger size pipe on the input or what? Maybe 1 1/4" or 1 1/2" any ideas. I can provide more details of the setup if needed.Thanks:confused: :mad:

[bertoni]

The drain calculator off the RC home page suggests about 1.25" pipe for that much flow. The closed loop is a bit different than a drain, but I'd still go for at least 1.25" for that size pump.