Quote Originally Posted by alex281
I followed the same size for my siphons at a half inch. the bed is about 50 gallons and takes about 5 minutes to drain flooded at 9 inches. stick with one size to keep things simple and be able to have more supplies in case of an emergency reconstruction. you never know when you might have to move things around and having everything the same size will be a big help. also, I doubt a 500 gph pump will lose efficiency if you use a size smaller. (could be wrong as I have no experience with 500gph pumps.) I say go with the 3/4
I agree with Alex281, except that I think you will find 1/2" is perfectly adequate. I've used 1/2" for my input water with pumps as large as 1200 gpm. I probably had some restriction at that size pump, but for a 500 gpm, it's perfectly adequate - even up to 800 gpm, 1/2" is fine. Plus it's cheaper, lighter, and easier to work with too.