Hi, we just had our vari flow xl replaced. This is my first time ever dealing with this type of valve and a sand filter. The pool has been filthy all season, so I'm looking at the valve, and the port on the valve marked "pump" goes to the pool return, and the port marked "return" goes to the pump. I'm assuming that this is the problem, but could someone confirm that it's important that the valve is plumbed in correctly? ie, I don't want the pool guy saying that the water flows the same way, it doesn't matter if it's installed backwards. thanks in advance for any help.