SCH 40 Pipe 3-1/2"(3.068 ID) X 4.0 OD – Des Moines Steel Inc.
PVC Conduit, 3-1/2 Inch Diameter, Schedule 40, 10 Feet | Crescent Electric Supply Company
Camco RV Easy Slip Elbow and 4-1 Adapter | Features a Larger Inside Diameter for Faster Dumping and Adapter Fits 3-Inch Slip or 3-Inch,3.5-Inch and 4- Inch Threaded Pipe (39144) - Walmart.com