The Navien 30010677A Water Inlet Filter is a replacement filtration component designed for use in compatible Navien tankless water heaters and combi boiler systems. It works by filtering sediment, debris, and other contaminants from the incoming water supply before it enters the heat exchanger and internal components. This helps maintain proper water flow and protects the system from ... https://www.partshnc.com/30010677a-navien-tankless-water-heaters-endlet-water-filter