I'm planning on doing an overflow with pvc pipe so I can set up my sump, I have my return pump that's 1200 GPH with 1" in/out. My question is what size pipe would be appropriate for the overflow to compensate for the return pump? would 1" be ok? anything I'm missing here. thanks
correction 1100 GPH sorry
You would probably be better of buying an overflow box rated for more GPH then the return pump. For example, and would want the PF-1800. You could definitely find one rated for the GPH on eBay for a lot cheaper. And Overflow boxes ensure that your carpet isn't flooded when the power goes out.
Is it 1100 at the head, or at the pump? Easiest way to test this (that I've found) is to get a one gallon jug, a 5 gallon bucket, and a stopwatch. Go in your driveway, fill the 5 gallon bucket with water and put the pump inside. Measure how high the head will be in your tank setup and keep it the same height while you're testing in the driveway. Have someone else hold the stopwatch and plug the pump in while you hold the jug and end of the hose at the appropriate height. Start the watch when the water starts flowing into the jug and stop the watch when the jug is full. I did mine 5 times to get a good average on the stopwatch. Then with some simple math you can figure out the gph flow rate and decide how big of an overflow box you need then.
My pump rated at 640gph flows about 400 with a 4ft head and 1" tube. I have an 800gph overflow box with a hofer gurgle buster that keeps it pretty quiet, despite several 90degree bends in my piping