Conduit Types: EMT, PVC, RMC & IMC

The four common raceways

The journeyman exam tests four conduit types repeatedly. Each is governed by its own NEC article and has a distinct set of permitted uses, mechanical properties, and grounding implications. The articles are:

• Article 342 — Intermediate Metal Conduit (IMC)
• Article 344 — Rigid Metal Conduit (RMC)
• Article 352 — Rigid Polyvinyl Chloride Conduit (PVC)
• Article 358 — Electrical Metallic Tubing (EMT)

These four are not the only raceways in the NEC — flexible conduit, liquidtight flexible, and others also appear — but they account for the large majority of wiring-method questions on the journeyman exam and are the starting point for understanding raceway selection.

Each conduit type: construction, use, and limits

EMT — Electrical Metallic Tubing (Article 358)

EMT is the thin-wall steel conduit that dominates light commercial and commercial construction. It is unthreaded, connected with set-screw or compression couplings and connectors, and lightweight enough to bend and cut on the job with standard tools. EMT is permitted in most dry, damp, and wet locations when listed fittings are used, including exposed, concealed, embedded in concrete, and in or under cinder fill. It is not permitted where subject to severe physical damage, and its use in hazardous locations is restricted to specific conditions and listed fittings.

Because EMT is metallic and continuous, a properly installed EMT run — with listed fittings making good metal-to-metal contact at every joint — is recognized as an equipment grounding conductor under NEC 250.118.

RMC — Rigid Metal Conduit (Article 344)

RMC is the heaviest and most protective metallic conduit. It is a thick-walled, threaded conduit with couplings and locknuts that make gas-tight joints when properly assembled. Article 344 permits RMC in virtually every location: wet, damp, corrosive environments (with appropriate coatings or fittings), direct burial, embedded in concrete, and in hazardous locations. When there is doubt about which conduit will pass an inspection, RMC almost always qualifies. It is also recognized as an EGC when properly installed.

The trade-off is labor: threading requires a pipe threader, and the weight makes handling larger sizes demanding. RMC is most cost-effective where its physical protection or burial-depth advantage justifies the additional effort.

IMC — Intermediate Metal Conduit (Article 342)

IMC occupies the middle ground between RMC and EMT. It is a threaded metallic conduit with a wall thinner than RMC but thicker than EMT, resulting in a lighter conduit that still accepts threaded fittings. Its permitted uses closely parallel those of RMC — wet, damp, corrosive (with appropriate protection), direct burial, and hazardous locations — making it a popular alternative where RMC's weight is inconvenient but EMT's thinner wall is insufficient. IMC is also recognized as an EGC.

PVC — Rigid Polyvinyl Chloride Conduit (Article 352)

PVC conduit is the dominant nonmetallic raceway. Schedule 40 is the standard grade; Schedule 80 has a thicker wall for areas subject to physical damage. PVC is highly resistant to corrosion and moisture, making it the default choice in wet and corrosive environments where metallic conduit would require constant maintenance. It is permitted for direct burial, embedded in concrete, and in exposed or concealed dry, damp, and wet locations.

PVC is not generally permitted in hazardous locations, in areas where ambient temperatures exceed the conduit's listing, or in locations where it could be subject to physical damage (unless Schedule 80 or specifically listed for the purpose). It also requires expansion fittings on long runs because PVC expands and contracts significantly with temperature changes.

Critical grounding point: Because PVC is nonmetallic, it cannot serve as an EGC under any circumstances. Every circuit in PVC conduit requires a separate equipment grounding conductor inside the raceway, sized to Table 250.122. This single rule separates PVC from all three metallic conduit types and appears on nearly every conduit comparison question on the exam.

Support spacing — metallic vs. nonmetallic

Support requirements differ meaningfully between metallic and nonmetallic conduit, largely because PVC expands with heat and requires more frequent anchoring to prevent sagging.

Conduit type	Typical max. support interval	Within how far of boxes / terminations
EMT (Art. 358)	10 ft	3 ft
RMC (Art. 344)	10 ft (size-adjusted for larger trade sizes)	3 ft
IMC (Art. 342)	10 ft (size-adjusted for larger trade sizes)	3 ft
PVC (Art. 352)	3 ft for small trade sizes; increases with larger sizes	3 ft

The 10-foot interval for metallic conduit is a reliable benchmark for exam questions. PVC's requirement is meaningfully more frequent for smaller sizes, reflecting the need to control thermal expansion. On a long horizontal PVC run, expect to see supports and expansion fittings both called out.

Conduit selection on the exam

Most conduit-type questions follow a scenario structure: a given environment, a required outcome, and four conduit choices. Work through them by elimination using the key differentiators:

• Hazardous location? Lean toward RMC or IMC. EMT has narrow permitted use there; PVC is generally excluded.
• Corrosive or wet environment? PVC is chemical-resistant; all types are permitted in wet locations with appropriate fittings, but PVC requires no coating maintenance.
• Ground path via conduit? Only metallic conduit qualifies. PVC always needs a separate wire EGC.
• Direct burial? RMC, IMC, and listed PVC are all permitted; the conduit type determines the required cover depth under Table 300.5.
• Physical damage risk? RMC gives the most protection; PVC Schedule 80 satisfies many exposed-location requirements; EMT is excluded where severe physical damage is likely.

Understanding the conduit fill rules is the other half of raceway work. How many conductors fit inside a given trade size of conduit is governed by Chapter 9 tables and Annex C. Use the conduit fill calculator to verify compliance, and review the conduit fill topic hub for the underlying rules.