An internal boss can have an outer side surface shaped to match the bored opening of the Drain, Waste, and Vent (DWV) pipe, an inner side surface shaped to align with an interior pipe surface of the sanitary Tee or Wye fitting component, and an internal face surface of the boss extending between the side surfaces and shaped to align with an interior pipe surface of the DWV pipe when welded thereto. Snap-fit wings can hold the interior face surface of the sanitary Tee or Wye fitting component against an exterior face surface of the DWV pipe while the fitting component and DWV pipe are homogeneously weldable into a single DWV fitting using a solvent mixture including a common plastic material. Related methods and single homogeneous fittings are also provided.