The WHB-1 wash basin features a self-closing waste valve designed to save space under the basin within cabinetry or furniture. The valve includes an internal membrane that opens under water pressure to allow wastewater to flow freely and then closes to form a seal, preventing foul odors and sewer gases from entering the building. It enables air intake into the discharge waste pipe during negative pressure conditions, eliminating the need for re-venting and offering greater flexibility in piping design. The valve requires no water seal and will not dry out due to evaporation or infrequent use, as the membrane remains closed. For maintenance, the valve can be cleaned without disassembling the piping—simply remove the cotter pin, take out the plug and membrane, clean with hot soapy water, then reassemble and secure the cotter pin in place. Specifications: 1 1/2 BSP female inlet nut x 1 1/4" universal compression outlet; overall height: 62 mm.