Abstract: An underdrain filter or strainer for use with power generation and ion exchange facilities, such as, but not limited to, deep bed demineralizers used in nuclear power plants deep bed ion exchangers. The filter is fabricated from a sintered, stainless steel mesh or wire-cloth filter media having a pore structure with pore size ranging approximately from one micron to two hundred microns. The filter media is composed of a plurality of filter media layers including a perforated inner core bonded to at least one drainage wire mesh, a filtration wire mesh, and a protective wire mesh forming an outer diameter, the layers being diffusion bonded to form a single monolithic laminate.