110-3(b) because it is in the UL listing. The white book says: "PVC conduit is designed to be connected to couplings, fittings, and boxes by the use of a suitable solvent type cement. Instructions supplied by the solvent type cement manufacturer describe the method of assembly and are to be followed." I have never seen instructions of electrical grade solvent type cement requiring the use of a primer. Also 347-6 requires the use of an "approved" method.