4" No Hub Cast Iron Double Combo Wye. Cast Iron Pipe is a premier piping system designed to withstands high temperatures and conditions. Cast Iron pipe and fittings are designed for drain, waste and vent (DWV) applications. No Hub fittings are designed to join cast-iron pipe together in DWV applicaitons. These no-hub fittings are not intended for use in high pressure applications. It is the most durable DWV piping system available and can be used in all types of construction. It's crush resistant, noncombustible and offers superior sound-deadening performance. This 4" No Hub Cast Iron Double Combo Wye is desinged to connect multiple lines together for increased flow and waste removal withing the water system.