Conduit selection is both a code question and a practical question. EMT (Electrical Metallic Tubing): the most common conduit for commercial and industrial indoor wiring. Easy to bend, relatively lightweight, pulls well, the metal raceway can serve as your EGC if properly bonded. Not suitable for direct burial or most outdoor below-grade applications.
Rigid Metal Conduit (RMC/GRC): the heavy-duty option. Required where severe physical protection is needed (parking garages, service entrance exposed to physical damage). IMC (Intermediate Metal Conduit) is between EMT and RMC - thicker wall than EMT, lighter than RMC.
Schedule 40 and Schedule 80 PVC: non-metallic, corrosion-resistant, suitable for direct burial and wet locations. PVC cannot serve as an EGC - you must pull a separate EGC. PVC expands and contracts significantly with temperature changes - support spacing and expansion fittings are important. Don’t use PVC in areas exposed to sunlight unless it’s UV-stabilized.