Your tank-type water heater develops a slow leak at the tank connection — and the fitting that should seal the heat trap nipple to the tank port keeps weeping past the Teflon tape. You pull it apart and find the washer has taken a compression set and no longer seals against the tank port face. Every tank-type water heater has these connections and eventually they need service. Flanged spud washer — the rubber-on-metal gasket that seals the heat trap nipple or spud connection to the water heater tank port. The bonded rubber-to-metal construction means the rubber sealing surface stays intact through the thermal cycling that breaks down standalone rubber washers. The metal flange gives it the structural support to handle threading torque without deforming, and the rubber face seals the port a Stocked at Crofton Lumber and Akron Lumber.