The WHB-1 wash basin features a self-closing waste valve that allows air to be drawn into the discharge waste pipe when negative pressure is present, eliminating the need to re-vent the discharge piping and providing greater flexibility in piping design. Designed to maximize space under the basin inside cabinets or furniture, this unit includes a 1 1/2 BSP female inlet nut and a 1 1/4 inch universal compression outlet. The internal membrane opens under water pressure to allow wastewater to flow freely, then closes to form a seal that prevents foul odors and sewer gases from entering the building. 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, clean with hot soapy water, then reassemble and secure the cotter pin in the provided slot. Overall height: 62 mm.