This McAlpine WHB-1 is a self-closing valve designed for wash hand basins and baths, helping to save space and prevent foul odors. It features a 1 1/4" BSP female inlet and a 1 1/4" universal compression outlet. The internal membrane opens under water pressure for discharge and closes to create a seal, preventing sewer gas entry. It also allows air to be drawn into the waste pipe during negative pressure, eliminating the need for secondary ventilation. The valve is easy to clean by removing the plug and membrane. Overall height is 62mm. It is manufactured in polypropylene and includes a side inlet connection for 19/23mm condensate or condense drain.