Pentair Genuine OEM O-Ring, Square 8.5 in. Closure

Pentair part 152509 is the square section o-ring for the 8.5 in. closure on Challenger high head and high flow pumps. It is the genuine Pentair part, and it also appears in the parts lists for several Triton side mount sand filters: the Triton II TR40, TR50, TR60, TR100 and TR140, the commercial TR100C and TR140C, and the Triton C-3.

Why the profile matters

The closure groove is cut for a square cross section. Fitting a round o-ring of roughly the right diameter tends to end in a lid that will not seal, air in the pump basket and a pump that struggles to hold prime. Replacing the o-ring with the correct square section part is the fix.

Installing it

Clean the groove, wipe a light film of silicone o-ring lubricant onto the new o-ring and seat it before closing the lid. Avoid petroleum based lubricants, which attack the rubber.