In or out of sump... can be easiely adjusted by a ball valve on the out tube(with oversized plumbing if possible. Example: 1/2" in 1" out with ball valve). IMO, the pump should be rated to move, at least 1x's the total water volume per hour, up to 5 or more. Mine is a diy and moves approx 750 gph on a 80 + true water volume system(nearly 10x's the true water volume). I have both a venturi air intake and dual air intake on an adjustable air pump with air stones.