An old or hardened O-ring in your whole-house water filter housing means water bypasses the filter cartridge entirely — sediment, rust, and particulates go straight through to your taps. You think you're filtering, but you're not. In rural water systems where cisterns and wells have inconsistent water quality, the O-ring seal is the one thing that determines whether the filter actually works. Replacement O-ring for HD-950 and HD-950A water filter housings. Precision-molded from durable rubber compounds engineered to hold a watertight seal under constant water pressure and through seasonal temperature swings — the O-ring doesn't dry out, crack, or compress set the way generic cord packing does. Key Specs Compatibility: HD-950 and HD-950A filter housings — verify O-ring ID and cross-section Stocked at Crofton Lumber and Akron Lumber.