ok, your talking closed loop. That is different. You just need use whatever size the intake on the pump takes. Output size can be reduced/create backpressure but you don't want to do that on the intake side. 4 1" outputs will not be much flow (jet wise, it will still be what your pump is rated at for the head pressure) unless you use an OM4way. I made my closed loop not for most jet type of flow, but most dispursed flow, just to add more movement in the tank and not use it as jets.