What is PVC Schedule 40 Conduit?
PVC Schedule 40 is rigid gray plastic conduit for underground and concealed wiring, governed by NEC Article 352. Cheap, corrosion-proof, cannot serve as EGC.
PVC Schedule 40 conduit is rigid gray polyvinyl chloride raceway widely used for underground feeders, concrete-encased ductbanks, and concealed building wiring. It is governed by NEC Article 352 and listed to UL 651. Schedule 40 has thinner walls than Schedule 80 but identical outer diameters, so fittings interchange. Because it is nonmetallic, PVC cannot serve as an equipment grounding conductor.
Construction
- Material: Rigid polyvinyl chloride (PVC)
- Color: Gray (sunlight-resistant formulation)
- Length: 10 ft and 20 ft sticks with bell-end couplings
- Joining: Solvent-welded with PVC cement
- Temperature: Listed for 90°C conductors per NEC 352.12(D)
The walls are thinner than Schedule 80, which gives Schedule 40 the larger interior cross-section of the two — important when sizing for conduit fill.
Interior cross-section (NEC Chapter 9 Table 4)
| Trade size | PVC Sch 40 area in² | PVC Sch 80 area in² |
|---|---|---|
| 1/2" | 0.285 | 0.217 |
| 3/4" | 0.508 | 0.409 |
| 1" | 0.832 | 0.688 |
| 1-1/4" | 1.453 | 1.237 |
| 1-1/2" | 1.986 | 1.711 |
| 2" | 3.291 | 2.874 |
| 2-1/2" | 4.695 | 4.119 |
| 3" | 7.268 | 6.442 |
| 3-1/2" | 9.737 | 8.688 |
| 4" | 12.554 | 11.258 |
Use these on the PVC conduit fill chart. For 3 or more conductors, multiply by 0.40 per NEC Chapter 9 Table 1.
NEC code reference (Article 352)
- NEC 352.10 — permitted uses: concealed, underground, corrosive environments, cinder fill, support of equipment
- NEC 352.10(B) — exposed locations subject to physical damage require Schedule 80
- NEC 352.12 — not permitted in hazardous locations (with exceptions), where exposed to physical damage with Schedule 40 alone, in patient care vicinity (some occupancies), or where ambient exceeds the conduit's listed temperature
- NEC 352.30 — supports within 3 ft of boxes; spacing varies with trade size (3 ft for 1/2"–1", up to 8 ft for larger)
- NEC 352.44 — expansion fittings required when length change exceeds 1/4 inch
Common applications
- Direct-buried feeders and branch circuits
- Concrete-encased ductbanks for service entrances
- Concealed wiring in concrete slabs
- Corrosive areas (chemical plants, wastewater treatment)
- Stub-ups from underground to outdoor equipment (use Schedule 80 for the exposed portion)
Trade-offs vs metal raceway
| Property | PVC Sch 40 | EMT | RMC |
|---|---|---|---|
| Material | Plastic | Steel | Steel |
| Direct burial | Yes | No | Yes |
| EGC qualifier | No | Yes | Yes |
| Corrosion resistance | Excellent | Moderate | Good |
| UV resistance | Sunlight-resistant listed | Moderate | Good |
| Expansion concerns | Significant | Minor | Minor |
| Field bending | Heat box required | Hand bender | Mechanical bender |
The biggest gotcha is thermal expansion — PVC expands roughly 4 inches per 100 ft per 100°F temperature swing. Long outdoor runs require expansion fittings sized per NEC Table 352.44(A).
Bending
PVC is field-bent with a hot box or torch (carefully), or with prefabricated factory bends (45°, 90°, sweeps). Minimum bend radius follows NEC Chapter 9 Table 2.
Quick reference
- Article: NEC 352
- Material: rigid PVC
- Underground: yes
- Physical damage: needs Schedule 80
- EGC qualifier: no — pull a separate EGC
- Color: gray