The Navien 20006947A O-Ring is a replacement EPDM sealing component designed for compatible Navien tankless water heaters. It works by creating a tight, leak-resistant seal between mating components, helping prevent water or fluid from escaping during normal operation. Made from durable EPDM material, this O-ring is suitable for use in plumbing and hydronic applications within support... https://www.partshnc.com/20006947a-navien-tankless-water-heaters-o-ring-epdm-p18-nsf-e7518-ewk2