An electrical conduit is a metal or plastic pipe that carries electrical wires from one point to another. It comes in rigid and flexible forms, and it protects the conductors inside from damage, moisture, and heat. Conduit shows up in exposed locations, such as along the surface of a wall, in unfinished areas like basements, crawlspaces, and attics, and in surface-mounted installations outdoors. The pipe is only half of the system; electrical grounding systems tie the installation to the earth through electrodes, conductors, bonding, and testing, and without them a conduit run is incomplete.
In all 50 states, the National Electrical Code, or NEC, is the benchmark for safe electrical design and installation. Its documentation spells out the requirements for a specific project, and local inspectors add their own expectations, so it pays to check with the local code enforcement agency and pull any required permits before work begins. Conduit work is also common when existing materials have worn, damaged, or become outdated. A permit also gives the job a second set of eyes: the inspector checks the conduit size, the support spacing, and the grounding connections before the power is turned on.
Where Conduit Is Used
Conduit protects wires in places where cable alone would be vulnerable. The NEC treats exposed and unfinished spaces differently from finished living areas, and that distinction drives most conduit decisions.
Exposed and Unfinished Spaces
Basement ceilings, crawlspaces, attics, and utility rooms are the classic conduit territory. Wires running along or across these surfaces can be struck by stored items, snagged during maintenance, or damaged by rodents, and the metal or plastic pipe shields them. In a garage workshop, conduit also makes future changes easy, because a new circuit can be pulled through the existing pipe instead of opening the walls.
Outdoor and Surface-Mounted Runs
Outdoors, conduit carries service to air conditioners, generators, and outbuildings, and weatherproof fittings keep water out of the raceway. Surface-mounted runs on masonry and concrete walls use conduit because there is no cavity to hide the wiring. Every run through the building envelope creates an opening, and air sealing electrical boxes and the surrounding framing stops drafts and keeps insulation effective.
- Exposed wall surfaces in basements and garages
- Attics and crawlspaces where cable would be unprotected
- Outdoor runs to AC units, generators, and outbuildings
- Surface-mounted runs on masonry and concrete
Types of Conduit
Five types of conduit cover nearly every residential and light commercial job. They differ in material, rigidity, cost, and the environments they tolerate. Conduit sizing follows the fill rules: the pipe must be large enough that conductors can be pulled without damaging insulation, and the code caps the number of wires per trade size. The fill tables in the code list exact numbers for each trade size.
| Type | Material | Typical Use |
|---|---|---|
| RMC | Galvanized steel | Heavy-duty and outdoor |
| IMC | Lighter steel | Outdoor and industrial |
| EMT | Thin-wall steel | Exposed interior runs |
| PVC | Plastic | Underground and wet |
| FMC and LFMC | Flexible metal, liquid-tight | Motor and appliance connections |
Trade sizes run from 1/2 inch up to several inches, and the label refers to the nominal inside diameter. A 1/2-inch conduit carries up to four 12-gauge wires under typical fill rules, while larger sizes handle heavier conductors or more circuits.
Rigid Conduit Options
Rigid metal conduit, or RMC, is the heavyweight: thick galvanized steel threaded at the joints, built for physical abuse and outdoor exposure. Intermediate metal conduit, IMC, uses thinner wall steel with the same threaded connections and weighs less. Electrical metallic tubing, EMT, is the everyday choice for exposed interior work; its thin walls bend easily with a hand bender and it installs fast.
Flexible and Plastic Conduit
Flexible metal conduit, FMC, and liquid-tight flexible metal conduit, LFMC, connect motors, disposals, and other vibrating equipment, where a rigid pipe would fatigue. PVC conduit is the standard for underground and wet locations; it never corrodes, but it needs expansion fittings where it crosses building joints. When planning a surface-mounted run, a detailed box and conduit layout guide shows how to measure, cut, and assemble the pieces in order.
Conduit vs. BX and Other Wiring Methods
Conduit is not the only way to route wires, and the choice between conduit and cable changes both the cost and the flexibility of the system. The choice also affects serviceability, because a raceway can be reused while buried cable cannot.
When the Code Requires Conduit
The NEC requires conduit in exposed locations, in areas subject to physical damage, and in most damp or wet locations. Commercial buildings lean heavily on conduit, while houses typically use cable inside wall cavities. Local amendments can tighten these rules, so the inspector’s office is the final authority. Most homeowners mix methods on a single project: cable inside the walls, conduit where the wiring is exposed.
Comparing Conduit to Cable
Conduit costs more in material and labor, but it lets you pull new conductors later without tearing into the wall. Cable, including NM cable and armored cable such as BX or MC, installs faster and costs less, but it is fixed once it is buried in the framing. Retrofit work often drives the choice: adding a circuit to a finished basement is far easier with conduit surface-mounted along the ceiling than with cable fished through closed walls. Matching the method to the situation is the core of residential electrical wiring, where methods, materials, and code-compliant installation all have to line up.
Fittings, Boxes, and Pulling Wire
Conduit is only as good as the boxes and fittings that connect it. Every joint, bend, and termination has to maintain the integrity of the raceway, and the boxes have to give the conductors room to terminate safely.
Choosing the Right Boxes
Metal boxes are the norm on conduit systems because they bond to the pipe and complete the grounding path. The box must be large enough for the number of conductors it holds; box fill calculations add up the wire volumes and compare them with the box capacity. Junction boxes also have to stay accessible, which means a permanently installed cover and clear access after the walls are closed. Choose boxes with knockout sizes that match the conduit trade size, so the fittings seat without adapters.
Pulling Wire Through Conduit
Pulling conductors through the pipe requires a fish tape, a lubricant rated for the wire insulation, and a plan for the bends. Pull points at the right intervals keep the tension low enough that the wire insulation survives the trip. Mark the pulling direction before you start, because pulling against the coil of the wire adds unnecessary resistance.
Keeping Bends Manageable
The total of all bends between pull points should stay under 360 degrees. Four 90-degree bends max out the allowance, and anything more makes the wire impossible to pull without damage. Installation best practices for EMT, IMC, RMC, and PVC, including bending and support spacing, are covered in a dedicated conduit systems guide.
Grounding a Conduit System
Grounding is what makes metal conduit safe. A properly bonded metal raceway carries fault current back to the panel, clearing the breaker instead of energizing the pipe.
Bonding the Conduit
Locknuts, bushings, and bonding jumpers tie every section of conduit to the grounding system at the service panel. Each connection has to be tight and corrosion-free, because a loose joint can turn the pipe into a shock hazard. Bonding also extends to the boxes, where the conductor path continues through the fittings. A bonding bushing is required where large conductors enter an enclosure, because the raceway needs a solid low-resistance path.
Equipment Grounding Conductors
Some inspectors require a green equipment grounding conductor pulled through the conduit in addition to the pipe bond, especially on long runs where the pipe alone might not be a reliable path. The grounding electrode system, driven rods and buried electrodes, connects the whole installation to the earth. Testing completes the job: a continuity check between the farthest box and the panel verifies that every joint is solid, and a ground-fault test on the first receptacle confirms the path works under load. Overcurrent devices work with grounding to protect people and property, and GFCI, AFCI, and surge protection complete the life-safety picture.
The choice between NM cable, MC cable, and conduit systems shapes the budget and the code path for an entire project. A comparison of electrical wiring methods shows where each approach belongs, from the cheapest cable in a dry wall cavity to a full conduit system in a basement, and that decision is best made on paper before the first box is mounted.