Pentair 11" Black Cartride Filter O-Ring

The Pentair 11" Black Cartridge Filter O-Ring is a specialized, model-specific elastomeric sealing gasket engineered for legacy Sta-Rite and Pac Fab pressurized pool and spa filtration systems, most notably the Sta-Rite Posi-Flo II cartridge series (including models PTM50, PTM70, PTM100, and PTM135) and select stainless steel separation tank assemblies. Molded from premium, high-density synthetic nitrile rubber (Buna-N), this heavy-duty circular gasket features an 11-inch inner diameter and a thick cross-sectional gauge. Its primary structural role is to seat securely within the matching perimeter groove where the upper and lower halves of the filter tank chassis interface. When the external heavy-duty tank clamp is tightened down, the rubber compresses to establish an absolute watertight and airtight pressure boundary. This vital seal allows the filtration vessel to safely contain high-velocity fluid flow and sustain continuous internal hydraulic operating parameters up to 50 PSI without weeping, leaking at the mid-seam, or experiencing catastrophic component blowout under pump vibration surges. Engineered to endure years of continuous mechanical compression, it completely resists degradation from outdoor weathering, extreme seasonal thermal shifts, and prolonged submersion in harsh pool chemicals like chlorine, bromine, and winterizing acid flushes. Due to its wide-diameter, thick-gauge solid rubber architecture, this individual main tank body O-ring carries a net product and shipping weight of approximately 0.35 to 0.45 pounds (about 5.6 to 7.2 ounces).