My buddy bought a house with a 1,700gallon pond drainging into a larger 3,000 gallon pond. Just finished cleaning it out, removing excess rocks and plants, replaced filter and pump, etc. Original there was no cover on the drain , just a 2" pvc pipe sticking out of the bulkhead. First we added one of those flat disc style drains, to help prevent fish/frogs from being sucked up. Worked fine. Then we added a T fitting and attached the no niche skimmer. But no water is being sucked thru the skimmer, only the bottom drain. The picture shows how it is setup. I was thinking the shut off vlave might need be between the bottom drain and the T and not between the skimmer and the T? Any ideas or better ways of setting it up? Figured id gather as much info as possible before i head back over there. Thank you for your time.