Originally Posted by bendavanza
What is the disadvantage of routing through the RIMS first?
March (and all centrifugal) pumps are not positive displacement. The do not create a positive vacuum on the back side of the pump and as such do not self prime. You can think of it as pushing the liquid, not pulling it. You want to push the liquid through the RIMS and any other components. It can work on the inlet side of the pump but is not ideal.
Coderage has his positioned this way and his system works for him. But in general, it is a bad idea to restrict the flow in any way before the pump. You want as much flow as possible to the pump, then restrict it (ball valve, RIMS, HERMS, Chiller, etc.) downstream.