NDS 475PR 4" PVC Back Water Valve with Riser is designed to protect low areas or basements from the backflow of waste from the street sewers. It is available in 2”, 3”, 4”, and 6” Hubs outlets; which fit 2”, 3”, 4” and 6” DVW and IPS pipe. The 3”, 4” and 6” Hubs may also be adapted to fit sewer and drain pipe with the use of NDS “DWV to Sewer and Drain Adapters” (2P41, 3P42, 2P43).