That would be easy enough, but I really wanted to not have any pumps or pipes in the tank.
I did another test with a new T, took a 1" line out of the side no valve or no return line from below going through. Pumped return water over the top of the tank, so there would be a clear drain just to see how much difference there would be. This worked pretty well, water level stayed about 2" above the overflow level. I'm working on a 1 1/2" T variation that I hope will work. If not I have ordered a 2" bulkhead & drill bit, but hope I don't have to use it. New test tomorrow.
Jim