Pentair .5" Black Rotor Shaft O-Ring

The Pentair 0.5" Black Multiport Valve Rotor Shaft O-Ring (Product #: 272421) is a factory-original OEM replacement elastomeric sealing element engineered to eliminate pressure-side water weeping and external air intrusion along the main control stem of pool and spa filtration networks. Specifically designed to seat securely within a precision-machined internal groove on the vertical central shaft of Pentair, Purex, and PacFab SM and SMBW series side-mounted diatomaceous earth (D.E.) separation valves—as well as select 1.5-inch and 2-inch top-mount multiport backwash configurations—this small yet critical ring forms a tight, dynamic mechanical barrier. When an operator depresses and rotates the external manual handle to index between filtration cycles (such as Filter, Backwash, Rinse, or Waste), the o-ring maintains an airtight seal against the inner walls of the valve dome cover while transitioning smoothly under heavy internal hydraulic loads. Molded from a premium-grade synthetic rubber compound featuring a 70-durometer hardness rating, this black elastomeric seal delivers exceptional dimensional compression memory and low-surface-friction resilience, allowing it to withstand continuous system line operating pressures up to 50 PSI. The rugged compound provides total immunity to structural dry-rotting, extreme pump room heat, and concentrated pool sanitizers like chlorine shock, muriatic acid, and advanced salt-chlorine generation. The physical dry weight of this single Pentair 0.5" Black Rotor Shaft O-Ring is approximately 0.005 pounds (roughly 0.08 ounces, with a nominal packaged envelope shipping weight of 0.05 pounds), offering a lightweight, crucial hardware standard to preserve hydraulic pressure efficiency and prevent dynamic fluid leaks.