A modular shower arm mounting system includes a water conduit and a replaceable shower arm assembly in sealing engagement therewith. The water conduit has a generally uniform inner wall and an outer diameter wall having a hexagonally or polygonally shaped drive force receiving area adjacent a threaded area. The conduit has one end attached to a manifold behind a shower wall surface and an outlet end projecting from the wall surface of sufficient length therefrom so that the drive force receiving area and threaded area are spaced from the wall surface. The replaceable shower arm assembly has an inner wall with a threaded portion for engagement with the conduit and a substantially smooth portion of gradually decreasing inner diameter downstream of said threaded portion approaching an outwardly projecting end thereof. The seal ring is adjacent the outlet end of the conduit to form a seal with the assembly. The shower arm assembly is replaceable without disconnecting the conduit from the manifold thereby allowing the user to easily change the shape and/or color of the visible shower arm assembly.