I have an elevated overflow spa with a "Pressure Imbalance" problem... The spa has four returns. I believe they are 1 1/4 or 1 1/2 ID diameter PVC pipes, and these PVC pipes are cut off flush with the spa walls. There is a pressure balance issue. When the Spa is run in "closed-loop mode" (no flow into the pool) one of the four returns, farthest from the pump, has virtually no output. The next pipe return closest to the pump is noticeable, decent, but not as strong as the two closest to the pump, which work well. Seems to me I have seen pipe inserts with threaded connections that can be mated to the existing spa return pipe...that have adjustable size screw-on "eyeballs" that can be screwed on to the newly installed threaded insert. Various size eyeball openings allow for back pressure to be created, thus evening out the flow across all four. I have not been able to find such a product, call it an adapter I guess. Any ideas? I would think I can simply use PVC cement, and push it in till the back of the threaded male flange is flush with the spa wall. The threaded female cap would screw on and allow for different size eyeballs to be installed.