Mag 12 Noise

[Baldy]

Hello,

I hope this forum was the right one for this question. I just set up my new sump in my basement with a mag 12 and started it circulating itself as i wanted to check flow through it. i have the mag 12 pumping through a manifold so i can regulate flow without choking off the pump, then through 10 feet of 1" flex hose, and back into where the overflow will be piped.

when i open the mag 12 all the way, it sounds as if there is air bubbles in the pump. the hum of the pump is no more than i expected, but the sound of air bubbles is quite loud. there is no head pressure on the pump at the moment, as its just returning to the other end of the sump. if i choke the pump back a bit though, the sound stops, and it just hums. I can only think that maybe its because this is a brand new pump and needs to break in.

any ideas?