Abstract: A heat trap assembly for providing a thermal dam within piping associated with water heaters is disclosed. The heat trap includes an elongated housing, a fin and a flap member. The housing includes first and second ends, and an interior opening extending therethrough to define an internal passage. The fin has a multi-sided body and is fixedly inserted into the housing. The flap member has a flexible disk-shaped body with first and second faces, an outer peripheral edge and an aperture disposed inward of the outer peripheral edge. A portion of the fin is inserted through the aperture. The outer peripheral edge is essentially contiguous with an interior wall surface of the housing in the absence of water flow within the internal passage, and is bendable in a direction of flow when water is flowing toward the first face or the second face.