Fleck 5600 & 9000 Tank O-ring (12281) - Repair Leaks on Water Softeners & Filter Systems Replacement tank O-ring for Fleck 5600 & 9000 softener & filter valves Replacement part for leaks that form where the control valve seals against the tank The O-ring (Fleck part# 12281) can become brittle, nicked or cut and allow leaks Genuine Fleck part