How to Install Metal Conduit?

Conduit offers superior protection and safety for wires. Even if local codes permit NM or armored cable in a basement, garage, attic, or crawlspace, consider installing conduit to protect wiring.

There are many different types and thicknesses of conduit. For most interior home installations, EMT (also called thinwall) is strong enough. Outdoors use intermediate metal conduit (IMC) or PVC conduit. Codes have detailed rules regarding conduit size, but generally 1/2-inch conduit is large enough for five or fewer wires; 3/4-inch conduit is used for more than five wires. When in doubt or if you might run more wire in the future, buy the larger size—it doesn't cost much more.

Metal conduit may serve as the path for grounding, or local codes may require you to run a green-insulated ground wire. If you use PVC pipe, you definitely need a ground wire, either green-insulated or bare copper. If there is no ground wire, make sure all the metal conduit connections are firm; a loose joint could break the ground path.

Save time by buying prebent fittings for your conduit. A coupling joins two pieces of conduit end to end. A sweep makes a slow turn, allowing wires to slide easily, while a pulling elbow makes a sharper turn. Setscrew fittings are commonly used with EMT conduit; they provide joints that are firm but not waterproof. For weathertight joints, use IMC conduit and compression fittings.

Oftentimes, it's easiest to just make a drawing of your proposed installation and have a salesperson help you assemble all the parts you need—conduit, sweeps, elbows, boxes, and clamps. And make sure to buy plenty of wire.