The WHB-1 wash basin features a self-closing waste valve designed to save space under the basin within cabinets or furniture. The valve includes an internal membrane that opens under water pressure to allow wastewater to flow freely and then closes to create a seal, preventing foul odors and sewer gases from entering the building. It allows air to be drawn into the discharge waste pipe when negative pressure occurs, 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 lack of use, as the membrane remains closed. For maintenance, the valve can be cleaned without disassembling the piping: remove the cotter pin, take out the plug and membrane, wash 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.