Thanks again for the good info.I found out how much the loss is.
1. If i have a ball valve on the return line restricting some flow, how would I know how much my pump is actually pumping to make my screen?
2. I have two options : I can use a tee on the return line with a valve at the tee putting the remaining water into the sump. Should I attach the screen at the Tee from the return line OR should I just attach the screen from the overflow box? Any performance loss/gain between the two?