An adjustable plumbing fitting has a piston rotatably and telescopically engaged in a housing, with one end of the housing adapted to be connected to a first plumbing part, and a cylindrical extension on the piston projecting from an opposite end of the housing and adapted to be connected to a second plumbing part. In one embodiment, two housings and associated pistons are integrally joined together to form a T-fitting for connecting the overflow and drain of a bathtub. In another embodiment, the housing is integrally formed with a J-shaped drain trap, and in another embodiment the housing and/or piston is integrally formed with a water closet flange.