Should skimmers and returns be plumbed with 1.5", 2", or 2.5" pipe, or something else? I will have two skimmers and 5 returns. Pump is a 3 HP Pentair VSF pump, model 011056. The pipes for my pool build were just delivered, and I'm seeing a combination of 1.5" pipes, 2" pipes, and 2.5" pipes.