Help, Size of Return Lines to use.

[kelemvor]

I believe in general, the bigger the pipe the better. If you're replacing pipes anyway, go with the bigger ones.

[nefretrameses]

I just replumbed part of my pool. 1 drain and 2 skimmers as well as a single return all 1 1/2 inch. I repiped the return with 2 inch and got a significant reduction in head loss. But in your case you have 3 supply lines to the pump and 5 returns. The amount of water in any one pipe is far less in terms of gallons per minute than in a single return setup like mine. Still, bigger is better and two 45 bends (or a sweep) is better than a 90. The $$$ difference is probably minimal.