Instead of a ball valve or gate valve you can just do a PVC stand pipe like euro-reef and many other skimmers use (snailman's counter current also use this technique). Replace the ball valve with a 90 facing up, add some pvc pipe to get to your final height (use coupler to make it adjustable), and then add another 90, a Tee, and then another pipe going back down into the pump (to reduce noise, bubbles). I believe this is called a Hartwell loop, or something along those lines. It costs $4 and is very adjustable and very accurate. Doesn't look as simple as a ball valve, but it does take up less sump space.