Three conduit types cover 95% of electrical installations: EMT, RMC, and PVC. Each is governed by NEC Article 358, 344, and 352 respectively. Picking wrong adds permit-review weeks, fails inspection, or quietly degrades over years until you have a bigger problem. Here's the working knowledge a contractor needs to make the call at the takeoff stage.
EMT — Electrical Metallic Tubing (NEC 358)
Thin-wall steel tubing, typically galvanized. Indoor, dry locations are EMT's natural home. EMT is by far the most common conduit in commercial buildings — light fixtures, branch circuits in walls and above ceilings, mechanical rooms, electrical rooms.
Strengths: cheap, lightweight, fast to install, accepts a huge variety of fittings (set-screw, compression, pull elbows). Most contractors install EMT 2–3× faster than RMC of the same trade size.
Limitations: not allowed in wet/damp locations without special EMT and corrosion-resistant fittings. NEC 358.10(B) restricts EMT in cinder concrete or fill, and NEC 358.10(D) requires specific listing for severe corrosive environments. Underground use of EMT is permitted only with corrosion-resistant fittings — typically PVC is a better call there.
RMC — Rigid Metal Conduit (NEC 344)
Thick-wall threaded steel. Heavy industrial, exposed exterior, hazardous locations, mechanical impact-prone areas. RMC is what you reach for when you need maximum mechanical protection or are working in hazardous (Class I, Div 1/2) locations.
Strengths: best mechanical protection, threaded couplings give better grounding continuity, accepted in virtually every NEC application including hazardous locations. Good corrosion resistance with proper coating (galvanized, PVC-coated rigid for severe corrosion).
Limitations: expensive, heavy, slow to install. RMC labor runs 1.8–2.5× EMT for the same trade size, plus the material cost. RMC threads need to be cut and reamed properly — a rushed job leaves sharp edges that damage conductors.
IMC (Intermediate Metal Conduit, NEC 342) is a thinner-walled cousin of RMC — good when you want better mechanical protection than EMT but lighter and cheaper than RMC. Threading is the same.
PVC — Schedule 40 and Schedule 80 (NEC 352)
Plastic conduit, the workhorse of underground and corrosive environments. Cantex and Carlon dominate the market in Arizona. Schedule 40 PVC is the standard underground wall thickness; Schedule 80 has thicker walls for above-grade exposed applications and where mechanical impact is a concern.
Strengths: impervious to corrosion, lightweight, easy to install with solvent-weld joints, accepted underground per NEC 300.5 with proper burial depth. Significantly cheaper than RMC for underground feeder runs.
Limitations: UV-degrades over years if exposed to direct desert sun (we replace 15–20 year old exterior PVC regularly in Phoenix). Heat-distorts above 90°C — not allowed in conduit runs that will see hot conductors at design temperature. Mechanical impact resistance is lower than metal.
For extreme environments — sewage, chemical plants, food processing — there's also RTRC fiberglass, but that's a specialty product we order on demand rather than stock.
Quick decision matrix
| Environment | First choice | Second choice | Avoid |
|---|---|---|---|
| Indoor commercial dry | EMT | IMC (high-traffic) | — |
| Underground feeder | PVC Sch 40 | RMC | EMT |
| Exposed exterior wall | RMC or IMC | PVC Sch 80 | EMT (corrodes) |
| Hazardous Class I | RMC threaded | IMC threaded | EMT, PVC |
| Wet/damp interior | EMT (corr-resistant fittings) | PVC | — |
| Solar combiner runs | PVC Sch 80 + UV jacket on conductors | RMC galvanized | EMT |
Pricing snapshot — Arizona, May 2026
Per 10 ft length, ¾" trade size, contractor pricing:
- EMT galvanized (Allied Tube): $5.50–$6.50
- IMC galvanized (Allied Tube): $11.00–$13.00
- RMC galvanized (Allied Tube): $14.00–$17.00
- PVC Sch 40 (Cantex): $3.20–$3.80
- PVC Sch 80 (Cantex): $5.50–$6.50
Larger trade sizes scale roughly linearly. Tech Energy America stocks Allied Tube and Cantex in trade sizes ½" through 4" with same-day or next-day availability for most jobs.
Common code traps in Arizona
- Burial depth. NEC 300.5 minimums vary by conduit type. PVC Sch 40 in residential lawns: 18". RMC in same location: 6". Inspectors will measure.
- Expansion joints. PVC has high thermal expansion. Long exposed PVC runs need expansion fittings every 50–100 ft per Cantex's tables.
- Bonding. EMT and IMC can serve as the equipment grounding conductor under NEC 250.118; PVC cannot — you need a separate green wire.
- Direct sun on PVC. Spec UV-resistant PVC for any above-grade exposed run, especially in Phoenix where summer surface temps exceed 60°C.
Related reading
- Conduit & fittings products we distribute
- Wire types — THHN vs XHHW vs MC
- More articles on the Tech Energy America blog
Need conduit and fittings priced for a project?
Send us your conduit takeoff and we'll quote against current Allied Tube and Cantex stock. Same-day quote for standard sizes.
📞 Call (480) 910-0867✉ Email Quote