The Fleck 2510 & 9100 tank O-ring (18303) is commonly replaced to fix leaks that develop at the base of the control valve where the valve seals against the tank. It may also be necessary to replace the slip ring (19197) if it is cracked, which will allow leaks in the same area. This is a genuine Fleck part that will work on all Fleck 2510 & 2510 SXT, softeners, filters, and air injection valves AND 9100 & 9100SXT softener valves, including the O-rings on the second tank adapter. Replacement tank O-ring for Fleck 2510 & 9100 softener & filter valves Replacement part for leaks that form where the control valve seals against the tank The O-ring (Fleck part# 18303) can become brittle, nicked or cut and allow leaks Genuine Fleck part
eBay