The NIBCO 3 in. x 3 in. x 1-1/2 in. x 1-1/2 in. ABS DWV All-Hub Double Sanitary Tee is designed for use with non-pressurized systems. The tee connects 2 branch lines into a vertical drain pipe. DWV is used for non-pressurized sanitary system Drain, Waste, and Vent. There are two types of DWV plastic: ABS (black plastic) and PVC (white plastic). The sanitary drainage and vent piping systems are installed to remove waste water and water-borne wastes from the plumbing fixtures and appliances. DWV also provides a circulation of air within the drainage piping. ABS (black) and PVC (white) plastic pipe and fittings have identical uses. The only reason for selecting one material over another is either the cost of the material or local plumbing code restrictions.