O-ring for Pentair BB10 or BB20 filter housing

O-rings for the Spectrum 717 pressure vessel are considered consumables because they can distort and harden over time, which makes it difficult to properly reseal the filter and can lead to leaks. A periodic change is therefore recommended, ideally when refilling the pressure vessel, to ensure a tight seal and prevent leaks. Before ordering a replacement set, you must verify the required size by measuring the groove's inner diameter on the sump's lip and the O-ring's thickness; confirm your measurements match the product dimensions of $138\text{mm}$ inner diameter and $5\text{mm}$ cross-section. When fitting the new O-rings, always apply silicone plumber's grease liberally to aid in seating and sealing.