We have about 8 returns on our 1975 concrete 35K gal 1hp pool, and 2 have good pressure, 4 have OK pressure, and 2 I think have no pressure. Our pool guy said that we need to buy a variety of "eyeballs" for the returns to equalize the pressure for proper circulation, as the pressure can run out of "oomph" as it gets further from the pump. Some eyeballs with smaller diameter and some with larger should even things out. The second pool guy said typically we would have back pressure on our plumbing system, so actually, the returns furthest from the pump would have the highest pressure, and the ones closest would have less. Either way, they said the solution was in the eyeballs.

Haven't tried this yet, as am waiting on latest repair man to come next week.