Despite the similarity to pipes used in plumbing, purpose-designed electrical fittings are used to connect conduit.
Box connectors join conduit to a junction box or other electrical box. A typical box connector is inserted into a knockout in a junction box, with the threaded end then being secured with a ring (called a lock nut) from within the box, as a bolt would be secured by a nut. The other end of the fitting usually has a screw or compression ring which is tightened down onto the inserted conduit. Fittings for non-threaded conduits are either secured with set screws or with a compression nut that encircles the conduit. Fittings for general purpose use with metal conduits may be made of die-cast zinc, but where stronger fittings are needed, they are made of copper-free aluminum or cast iron.
Couplings connect two pieces of conduit together.
Sometimes the fittings are considered sufficiently conductive to bond (electrically unite) the metal conduit to a metal junction box (thus sharing the box’s ground connection); other times, grounding bushings are used which have bonding jumpers from the bushing to a grounding screw on the box.
Unlike water piping, if the conduit is to be watertight, the idea is to keep water out, not in. In this case, gaskets are used with special fittings, such as the weatherhead leading from the overhead electrical mains to the electric meter.
Flexible metal conduit usually uses fittings with a clamp on the outside of the box, just like bare cables would.