A Guide to Selecting Electrical Conduit


A Guide to Selecting Electrical Conduit

Simply put, conduit is used to protect electrical wire and cable. However, all conduits are not created equal! There are different types, each suited for specific conditions and applications, and each with its unique advantages. Understanding these differences will help in selecting the right conduit for the job. Keep in mind, the uses discussed in this article are based on the National Electric Code. Local building codes vary and not all conduits discussed here meet code in all areas. Always check your local codes before beginning a project.



Metallic Conduit

Rigid Metal Conduit, or type RMC, is most commonly known as "rigid." It has long been the standard for providing superior protection from severe physical and environmental damage. Galvanized steel RMC is factory-threaded at both ends, and has a coupler applied on one end.

Advantages and uses: May be used for exposed or concealed applications, indoors or outdoors, in wet or dry conditions, and may be buried directly in earth or in concrete. It is also permitted as an equipment grounding conductor.

Disadvantages and limitations: Heavy, and usually more expensive than alternatives. In addition, the fittings tend to be more expensive. Bending rigid conduit is difficult, and requires special equipment for sizes larger than 3/4". If cut, it may need to be rethreaded, unless compression fittings are used.

Sizes available at Menards®: 1/2"x10', 3/4"x10', 1"x10', 1-1/4"x10', 1-1/2"x10', 2"x10' SKUs: 365-6286-6338*


Electrical Metallic Tubing, or type EMT, is far and away the most commonly used type of conduit. (Note: Technically speaking, EMT is not classified as conduit; it's tubing.) It's commonly known as "thinwall" because the wall is much thinner than RMC. As a result, it's not suitable for use where it's likely to be subject to severe physical damage, for example, on a wall next to a driveway. Like steel RMC, EMT is galvanized to provide excellent rust and corrosion resistance.

Advantages and uses: Lightweight and easy to bend. Fittings are commonly available and inexpensive. It may be used for exposed or concealed applications, indoors or outdoors, in wet or dry conditions, and may be buried directly in earth or in concrete. It is also permitted as an equipment grounding conductor.

Disadvantages and limitations: Not suitable for use where subject to severe physical damage.

Sizes available at Menards®: 1/2"x5', 1/2"x10', 3/4"x5', 3/4"x10', 1"x10', 1-1/4"x10', 1-1/2"x10', 2"x10' SKUs: 365-1332-1427*



Flexible Metallic Conduit, or type FMC, is more commonly known as "flex" or "Greenfield." It's manufactured from an interlocking, spirally wound metal strip. Although the length of installation is not limited, it's used most commonly for the last several feet of a more conventional conduit system that would be difficult to terminate. For example, to connect light fixtures in a suspended grid ceiling. It's also used for equipment which is subject to movement or vibration, such as pumps or manufacturing equipment.

Advantages and uses: Easy to install, and no special equipment is needed; however, use of a cutting tool is highly recommended as it will save time and yield the best results. May be used for exposed or concealed applications in dry locations only. Where flexibility is not required after installation it is permitted as an equipment grounding conductor. (Note: Installations that are subject to vibration or that require a high degree of flexibility require a separate equipment grounding conductor.)

Disadvantages and limitations: May not be used in wet locations, in corrosive environments, or where subject to severe physical damage.

Sizes available at Menards®: 3/8"x25', 3/8"x50',3/8"x100', 1/2"x25', 1/2"x50', 1/2"x100', 3/4"x25', 3/4"x50', 3/4"x100', 1"x50' SKUs: 365-4123-4265*



Liquidtight Flexible Metallic Conduit, or type LFMC, is commonly known as "liquidtight" or "sealtight." Like FMC, LFMC is made with an interlocking, spirally wound metal strip; however, it has an overall outer covering of liquidtight, sunlight-resistant, non-metallic material. Also like FMC, length of installation is not limited, and it's used most commonly for the last several feet of a more conventional conduit system that would be difficult to terminate, and for equipment that's prone to movement or vibration. It's an excellent choice for environments with dust, vapor, or moisture.

Advantages and uses: Easy to install, and no special equipment is needed; however, use of a cutting tool is highly recommended as it will save time and yield the best results. May be used for exposed or concealed applications, indoors or outdoors, in wet or dry conditions, and may be buried directly in earth. Where flexibility is not required after installation it is permitted as an equipment grounding conductor. (Note: Installations that are subject to vibration or that require a high degree of flexibility require a separate equipment grounding conductor.)

Disadvantages and limitations: Not for use where subject to severe physical damage.

Sizes available at Menards®: 1/2"x10', 1/2"x25', 3/4"x10', 3/4"x25' SKUs: 365-4181-4217*



Nonmetallic Conduit

Rigid Polyvinyl Chloride Conduit, or type PVC, is most commonly available with one end belled, to facilitate joining sections together without need for a separate coupler. Both the conduit and pre-formed elbows are available in both schedule 40 and schedule 80. Schedule 40 has a thinner wall than schedule 80, and is not permitted for use where subject to physical damage. The outside diameters of schedule 40 and schedule 80 conduit are identical; therefore, the same fittings are employed for both. Conduit and fittings are joined by solvent welding with primer and cement. Because PVC is prone to thermal expansion and contraction, use of expansions couplings is necessary where the total run length will change by 1/4" or more.

Advantages and uses: Nonconductive, flame retardant, and sunlight resistant. Inexpensive and easy to install. No special equipment is needed. May be used indoors and outdoors, for concealed or exposed work, and in dry, damp, or wet conditions. It's also suitable for corrosive conditions, for direct burial, and encasement in concrete. As previously noted, schedule 80 is suitable for use where subject to physical damage.

Disadvantages and limitations: Not suitable for hazardous locations, or where ambient temperature exceeds 50° C (122° F). Because it's nonconductive, it may not be used as an equipment grounding conductor. Where equipment grounding is required, a separate equipment grounding conductor must be installed within the conduit.

Sizes available at Menards®:
Schedule 40
In 5' lengths: 1/2", 3/4"
In 10' lengths: 1/2", 3/4", 1", 1-1/4", 1-1/2", 2", 2-1/2", 3", 4", 5", 6"
In 20' lengths: 1/2", 3/4", 1", 1-1/4", 1-1/2", 2", 2-1/2", 3", 4", 5"
SKUs: 365-2072-5418*
Schedule 80
In 10' and 20' lengths: 1/2", 3/4", 1", 1-1/4", 1-1/2", 2", 2-1/2", 3", 4", 5", 6"
SKUs: 365-2054-5419*



Liquidtight Flexible Nonmetallic Conduit, or type LFNC-B, is also commonly known as "liquidtight" or "sealtight." It has a smooth, seamless inner surface with integral reinforcement within the conduit wall. It's made of a liquidtight, sunlight-resistant, non-metallic material. Although the maximum length of installation is not limited, and it's used most commonly for the last several feet of a more conventional conduit system that would be difficult to terminate, and for equipment that's prone to movement or vibration. It's an excellent choice for environments with dust, vapor, or moisture.

Advantages and uses: Nonconductive, flame retardant, and sunlight resistant. Easy to install, and no special equipment is needed. May be used indoors and outdoors, for concealed or exposed work, and in dry, damp, or wet conditions. It's also suitable for direct burial, and encasement in concrete.

Disadvantages and limitations: Not suitable for hazardous locations, where subject to physical damage, or where the operating voltage of the conductors is greater than 600 volts. Because it's nonconductive, it may not be used as an equipment grounding conductor. Where equipment grounding is required, a separate equipment grounding conductor must be installed within the conduit.

Sizes available at Menards®: 1/2"x25', 1/2"x100', 3/4"x25', 3/4"x100', 1"x50' SKUs 365-4521-4555*



Electrical Nonmetallic Tubing, or type ENT, is a pliable, corrugated raceway of moisture-resistant, chemical-resistant, flame-retardant, non-metallic material. Though not specified by code, it's commonly light blue in color. There are fittings designed specifically for use with ENT; however, common PVC conduit fittings may be used with solvent welding.

Advantages and uses: Nonconductive and flame retardant. Easy to install, and no special equipment is needed. May be used indoors for concealed or exposed work, in dry, damp, or wet conditions. It may also be encased in concrete.

Disadvantages and limitations: Not suitable for outdoor use, direct burial, in hazardous locations, where subject to physical damage, where ambient temperature exceeds 50° C (122° F), or where the operating voltages of the conductors is greater than 600 volts. Because it's nonconductive, it may not be used as an equipment grounding conductor. Where equipment grounding is required, a separate equipment grounding conductor must be installed within the conduit.

Sizes available at Menards®: 1/2"x 10', 1/2"x200', 3/4"x10', 3/4"x100', 1"x10', 1"x100' SKUs: 365-4602-4595*

Come into Menards® Electrical department to find the proper conduit for all your electrical and building projects!

*Not all products listed are available in all stores. Special order is available.