Types of Conduit and When to Use Each

EMT, the everyday raceway

Electrical metallic tubing, EMT, is thin-wall steel and the workhorse of commercial interiors. It is light, cheap, bends easily with a hand bender, and installs fast with set-screw or compression fittings. Use it in dry, protected indoor locations and exposed runs that will not take physical abuse.

It is not rated for direct burial and needs the right fittings to be used outdoors or in damp spots. Where it can get hit, step up to something tougher.

Rigid and IMC for tough spots

Rigid metal conduit, RMC, and intermediate metal conduit, IMC, are thick-wall threaded steel. They take physical abuse, work outdoors, and can be buried. Use them where the raceway needs mechanical strength: service masts, exposed exterior runs, and areas with impact risk.

They cost more and take more labor to thread and bend, so you reserve them for where that toughness earns its keep.

PVC and where it shines

Rigid PVC conduit is nonmetallic, corrosion-proof, and the default for underground and wet or corrosive environments. It is cheap and glues together fast. Because it is nonmetallic, you must run a separate equipment grounding conductor inside it; the conduit cannot serve as the ground path.

• Underground feeders and service laterals.
• Corrosive areas like wash-down and chemical rooms.
• Remember expansion fittings on long exposed outdoor runs; PVC moves with temperature.

Flexible types for the last stretch

Flexible metal conduit, FMC or Greenfield, and liquidtight flexible conduit, LFMC, let you make the final connection to things that vibrate or move, like motors and rooftop units. Liquidtight adds a plastic jacket for wet and outdoor locations.

Keep flex runs short, support them per the code, and watch the length limits when you rely on the flex for grounding. For a motor that shakes, a short liquidtight whip is exactly the right tool.