An electrical conduit is a tube or pipe that protects electrical cable in buildings, structures, outside, or underground. Conduits can be made of metal, plastic, or other materials.

Some types of wiring are generally required to be run in the conduit at all times, such as THHN/THWN. In other cases, the use of conduit can be required by the National Electric Code or local codes.

The purposes of an electrical conduit include protecting wires and cables from damage, reducing the risk of fire, or keeping the wires organized. This guide will help you distinguish between metal and non-metal conduits, including RMC, IMC, EMT, and PVC, among others.

Metal Conduits

Metal conduits are considered more durable. They offer excellent protection from EMI and can also be used as grounding paths. However, these conduits are more expensive and generally harder to install.

Rigid Metal Conduit (RMC)

RMC is a thick, heavy-duty, galvanized steel or aluminum conduit with threaded fittings. It offers high protection against impacts.

This conduit is often used outdoors as it offers protection from damage and structural support to cables and other equipment. RMC may also be used as an equipment grounding conductor with additional accessories.

Due to bulky construction, rigid metal conduit protects against fire. However, the conduit is heavy-weight and can be difficult to work with.

It's often used in commercial buildings, industrial settings, or underground installations. Opting for an RMC conduit made of galvanized steel is best for corrosion.

Best For: Outdoor Installations That Require Mechanical Protection

Intermediate Metal Conduit (IMC)

Similar to RMC, IMC is a lighter and thinner conduit, making it easier to install. Still, it is approved for all the same applications as RMC. IMC conduit is also cheaper compared to its counterpart.

IMC is available in both threaded and unthreaded variations. It can also be coated.

It is used in both exposed and concealed work in harsh environments, such as manufacturing facilities and industrial plants. Because it is easier to install, new constructions often opt for this type of conduit.

Best For: Outdoor Installations for New Construction, Industrial Facilities.

Electrical Metallic Tubing (EMT)

 This thin-walled conduit, known as "thin-wall," is made of coated galvanized steel or aluminum. It's easy to bend and work with, making it popular for indoor applications, but it's not as protective as RMC or IMC. Though still considered rigid, this type of conduit is easy to bend.

This type of conduit is not threaded and is installed with the help of couplings and fittings. It cannot be installed in applications subjected to mechanical damage. While it is generally fine for both exposed and concealed applications, it should use watertight fittings for exposed ones.

Best For: Indoor Wiring in Residential and Commercial Buildings

Flexible Metal Conduit (FMC) and Liquid Tight Flexible Metal Conduit (LFMC)

 Known as "Greenfield" after its creator or "flex," this conduit is made of a helically-wound, flexible metal strip in the form of a spiral. It's often used in areas where rigid conduits, such as tight corners or complex routes, would be difficult to install. For example, FMC is used in dry indoor locations when connecting a wall box to a garbage disposal. The conduit is not often used outdoors because it needs airtight qualities. 

There is also a lighter version of this conduit, liquid tight flexible metal conduit (LFMC), which has a waterproof plastic coating that seals it from moisture. This type of conduit is used with outdoor units, like air conditioners.

FMC and LFMC should not be exposed to mechanical damage.

Best For:

FMC - short indoor complex routes

LFMC - outdoor routes in residential buildings

Non-Metal Conduits

Non-metal conduits have greater corrosion resistance and perform better in corrosive and damp environments. They are also lighter and easier to install compared to their metal counterparts. Non-metal conduits are usually less expensive than metal conduits, making them a cost-effective choice for many installations.

PVC Conduit

PVC is a lightweight, corrosion-resistant plastic conduit resembling a plain plastic pipe. It's often used for underground installations due to its resistance to moisture and chemicals, but it's also used in exposed locations.

PVC conduit is bent after being heated. Variations of PVC conduit are watertight, which makes the cable suitable for direct burial applications.

PVC conduit exists in rigid and flexible variations. Rigid PVC is best for underground or outdoor applications, while flexible PVC works best for complex routing and tight corners while not providing as much protection.

Best For: All sorts of applications, including outdoor, complex routing, and direct burial. However, watch for high-temperature impact.

PVC is often compared to metal conduit, namely to EMT. While both are thin-wall conduits, EMT can serve as a grounding path, while PVC does not. PVC has a better ability than EMT to survive environmental degradation. PVC can be both flexible and rigid, while EMT is always semi-rigid. PVC is worse than EMT at tolerating high heat.

EMT is typically used indoors where it won't be exposed to corrosive conditions. It's common in commercial and industrial buildings. PVC, on the other hand, is often used for outdoor, underground, or concrete-embedded applications due to its corrosion and moisture resistance

Rigid Nonmetallic Conduit (RNC)

 RNC is unthreaded smooth conduit made of high-density polyethylene or RTRC (fiberglass). Similar to PVC conduit, RNC is resistant to moisture and corrosive environments. It's often used in exterior and underground installations.

RTRC is one of the most effective materials for conduits on the market. It has high-temperature resistance, UV resistance, and excellent corrosion resistance. It's also lightweight in addition to other benefits.

Best For: Versatile interior and exterior applications.

Electrical Nonmetallic Tubing (ENT)

Also known as a "smurf tube" due to its blue color, ENT is a flexible plastic conduit used in walls, floors, and ceilings. It's popular for residential use due to its flexibility and ease of installation. 

ENT conduit is unsuitable for exposed locations as it performs poorly in UV. It is extremely flexible, and, unlike PVC, can be bent without heat applied to it.

Best For: In-wall, floors, and ceilings.

Liquid Flexible Nonmetallic Conduit (LFNC)

This flexible conduit is often used in tight corners and complex routes where rigid conduit would be difficult to install. LFNC is watertight. 

Best For: Outdoor Installations and Areas Around Sinks or Other Water Sources.