Pentair O-Ring | System 3 Modular Media Filter | 35505-1428Z

Description

The Pentair 35505-1428Z is the OEM replacement large bulkhead and elbow O-ring for the Sta-Rite System 3 Modular Media SM Series D.E. filter. This single O-ring seals the bulkhead and elbow connections within the filter housing, preventing water bypass and maintaining system pressure integrity.

⚠️ IMPORTANT: LUBRICATION REQUIRED — SOLD SEPARATELY
Always lubricate this O-ring with a silicone-based lubricant before installation. We carry the Pentair R172351 Lifeguard® Silicone Lubricant — the OEM-matched product for Pentair equipment.

This O-ring seats at the large bulkhead and elbow junction points inside the System 3 filter. When this seal degrades, water can bypass the filtration media or leak externally at the connection points. Replacing it restores a proper pressure-tight seal. Match the part number on your existing O-ring before ordering — this is the large bulkhead/elbow size, not the smaller O-rings used elsewhere in the filter assembly.

Specifications

Fits Into

Compatibility is based on Pentair parts documentation and available OEM records. This is not an exhaustive list. For certainty, verify the part number in your equipment’s manual or on the original part itself before ordering.

Pro Tip

When servicing the System 3 filter, inspect all O-rings in the assembly — not just the one showing visible wear. The bulkhead and elbow O-rings are subject to the same pressure and chemical exposure cycles, so replacing them together during the same service visit avoids a repeat teardown. Before installing this O-ring, apply a thin, even coat of Pentair R172351 Lifeguard® Silicone Lubricant to help it seat evenly and resist tearing during reassembly. Never use petroleum-based lubricants — they will degrade the rubber and shorten the seal’s service life.