the valve furthest away from the furnace is fed by two skimmers. The 5 lines above that valve feed the 5 returns. Previously, the valve returning suction from the skimmer would be wide open to allow equal section. I adjusted it late last year to gain more section to a particular skimmer but if I return the valve to the open position, water is blocked. It works fine in this position or if I go to the other side. Oddly, it doesn’t open close freely like the other valves.