I have a built in fuge in my sump but needed an external feed. I first hooked up an extra pump, more money, cords, and heat.. When I got my huge Eheim hooked up it was far to much out put into my tank so I decided to cut down on the flow. I read putting a ball valve on the return side doesn't hurt the pump. I'm a pipefitter and I know better than that. So instead what I did was to add a tee into my return above the sump and add a ball valve on the diverted side of the tee. I then piped from that to the fuge. Instant success. i can control the amount water returning to my tank by diverting it to my fuge, vice versa as well. Noi extra head pressure was added to my pump so it works freely and all is well.