Schedule 40 Vs. 80 Electrical Conduit: Which One Is Better?

Dennis Howard
by Dennis Howard

PVC conduit has many uses in both new construction and remodel construction for residential and commercial applications. Typically, PVC electrical conduit is available as schedule 40 or schedule 80. Each has s specific set of uses, and local building codes usually specify these applications.

Schedule 40 PVC conduit has a thinner wall than schedule 80 PVC conduit. Both Schedule 80 and 40 PVC have the same outside diameter. The smaller inside diameter of the schedule 80 PVC conduit allows less room for pulling wire through the conduit with the same outside diameter. In addition, there are other building code requirements for using PVC conduit.

Determining which PVC conduit to use on a job is often specified by the architect or engineer. In some cases, where no formal plans are available, it is necessary to know the local building code requirements for installing PVC conduits. In addition, you must install PVC conduit correctly to preserve the waterproof and insulating properties of the PVC conduit.

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Different Types of PVC Conduit

PVC conduit comes in several different styles and types. The scheduling on PVC pipe is an indication of the wall thickness of the pipe. When speaking of PVC conduit, the schedule rating has nothing to do with pressure capabilities or testing. The different styles of PVC electrical conduits have different characteristics and use.

Schedule 40 PVC Electrical Conduit

According to the National Electrical Code (NEC), 352 gives the specifications for using all electrical conduits and PVC electrical conduit especially. NEC 325 speaks to the use of schedule 40 PVC electrical conduit for:

  • Uses in walls, floors, and ceilings
  • Installation below ground
  • Encasement in concrete
  • Exposure to direct sunlight

The NEC 325 specifications speak in detail about using schedule 40 PVC in these situations. If you anticipate using schedule 40 PVC electrical conduit in these situations, you should familiarize yourself with the NEC code requirements.

Schedule 80 PVC Electrical Conduit

Schedule 80 PVC electrical conduit differs from schedule 40 conduit in one way. Schedule 80 PVC conduit has thicker walls than schedule 40 PVC conduit. This thicker wall structure provides more resistance to damage when installing conduits in high traffic or high hazard areas.

Generally, schedule 80 PVC conduit is useable in any situation where schedule 40 conduit is applicable. When used above ground, schedule 80 PVC conduits are required by the NEC for installation where physical damage is possible, and the extra wall thickness is needed for safety reasons. (See NEC 352.10(F))

PVC Utility Duct

PVC utility duct is for use underground or in encased applications. Utility duct is not appropriate for use in walls, floors, or ceilings in residential or commercial structures. Utility ducts may contain separate PVC conduit installations or bundled cable runs.

ENT Electrical Non-Metallic Tubing

Ent is a flexible PVC alternative for rigid metallic electrical conduits. This material is easier to handle, lighter, and quicker to install than most rigid metallic tubing. ENT flexible tubing is suitable for use in ceilings, walls, and floors. ENT flexible tubing is useable for concrete encasement when the proper fittings and solvents preserve the PVC material properties.

Why Use Conduit and not Romex?

Electricians commonly use Romex to run electrical services inside residential structures. Sometimes it is necessary to use conduit to protect the wiring from potential hazards or damage. In these cases, the common practice is to run THHN or THWN wire inside the conduit. To save money, electricians tend to use the most economical method of running electrical services. Electricians install conduits when the building code specifies its use.

The Pros and Cons of PVC Electrical Conduit

PVC electrical conduit offers many advantages to electricians and builders. It also has its downsides to consider when specifying VC conduit in a building plan. Every electrician or do-it-yourself homeowner should understand the advantages and disadvantages of using PVC conduit.

PVC Electrical Conduit Advantages

  • PVC conduit is lighter in weight than metallic tubing conduits.
  • It is easier to install a PVC conduit. You can cut PVC conduit with hand shears. Joints can be made watertight using the appropriate primer and solvent for the type of conduit.
  • In general, a PVC conduit is cheaper per running foot than a rigid metal conduit.
  • In situations where exposure to chemicals, saltwater, and other materials is a problem for metal conduit, PVC conduit offers superb resistance to these materials.
  • PVC conduit is flexible to a certain degree, making some installations easier.

PVC conduit is not without its disadvantages. These disadvantages must be understood when installing a PVC conduit.

  • Long runs of PVC conduit require more support than comparable runs of rigid conduit otherwise, the conduit will sag, making it a potential snag hazard.
  • PVC conduit is non-conductive. Most installations using PVC conduit require an extra green wire in the PVC conduit for grounding purposes. This extra wire adds cost and time to the project.
  • In high traffic or hazard areas, PVC conduit is more susceptible to damage from normal daily activities.

PVC conduit offers flexibility, speed of installation, and resistance to many chemicals and environmental hazards at a reduced cost. These features make PVC conduit popular with architects, engineers, and electricians. Homeowners like the lower effective cost of PVC conduit.

Don’t Confuse PVC Electrical Conduit with PVC Plumbing Pipe

Some do-it-yourselfers are under the mistaken assumption that PVC electrical conduit and PVC plumbing pipe are interchangeable. Nothing could be further from the truth. PVC plumbing pipe is built to different standards and must undergo much more rigorous testing than PVC electrical conduit.

PVC Plumbing Pipe – Pressure Counts

PVC plumbing pipe is the same basic material as PVC electrical conduit. However, the standards to which PVC plumbing pipe is manufactured are much more stringent. The specifications and requirements for PVC conduit and PVC piping have some distinct differences.

  • Pressure Testing – PVC electrical conduit does not undergo any pressure testing. PVC plumbing pipe carries pressure ratings tested by independent testing laboratories. Manufacturers print these maximum working pressures on the PVC plumbing pipe as part of the labeling process. PVC electrical conduit doesn’t carry this pressure labeling.
  • Heated water rating – PVC plumbing pipe also carries a maximum temperature rating. PVC electrical conduit isn’t tested for pressure or temperature, nor does it carry any temperature labeling.
  • Food grade ratings – Typically, PVC piping I rated for domestic potable water use. PVC electrical conduit isn’t rated for potable water use and doesn’t have the labeling required to make it acceptable for domestic water uses.

Different Uses, Different Designs

PVC electrical conduit fittings often fit PVC plumbing pipes and vice versa. However, there are differences in the fittings that can cause problems if the fittings are used incorrectly. The design of electrical conduit fittings allows the wire to be easily pulled through the fittings. Often the radius of elbows is larger than comparable plumbing fittings.

Using plumbing fittings in electrical conduit installations can cause problems running wire and making good joints at the fittings. Conversely, conduit fittings in a plumbing installation may more easily leak or fail than the right plumbing fittings.

Installing PVC Conduit the Right Way

As simple as it may seem to install a length of PVC electrical conduit, there are some tips and tricks that can make the job easier in the long run. These steps can help you through the process of running the length of the PVC electrical conduit, installing a box, and pulling the wire through the conduit.

Step 1: Gather Your Tools and Materials

Before you begin, make sure you have all the necessary tools and parts to complete the project. Having everything in one place when you start reduces frustrations. You also avoid delays from stops required to locate and secure parts or tools during the project. In general, to install a PVC electrical conduit run, you will need:

  • Enough PVC conduit to complete the job
  • The fittings necessary to make corners or terminate the PVC electrical conduit at the ends of the run
  • Any electrical boxes, outlets, or other fittings
  • PVC primer and solvent
  • A PVC cutting tool such as a hacksaw, backsaw, or a pair of PVC shears
  • A utility knife to clean burrs or shavings from the cuts on the PVC electrical conduit
  • The proper size wire to make the electrical connections. THHN wire is the preferred wire for pulling through an electrical conduit. Its plastic insulation slides easily through the PVC conduit without the need for lubricants.
  • Wire cutters or linesman pliers
  • A wire snake for longer PVC conduit runs. Using a snake will make pulling wire faster. You can often pull a wire bundle through the conduit at one time rather than pulling each wire individually.

Step 2: Install any Electrical Boxes in the Circuit.

Locate where you want your electrical service boxes to old switches or outlets. Secure these boxes according to the manufacturer’s recommendations. You should always install your new circuits with the building code in mind.

Step 3: Install the Appropriate Connectors in the Boxes.

Take out the removable plugs on the boxes and install the correct connectors into the holes. Typically, the threaded end of the connector goes into the hole in the box. A rubber gasket and a threaded nut lock the connection into place and create a watertight joint.

Step 4: Measure, Cut, and Glue the PVC conduit in place.

Measure the correct length and transfer the measurement to the PVC electrical conduit. Make sure you allow for the length of the conduit that fits into the fittings on the end. Use a hacksaw, backsaw or PVC cutting shears to make the cut. Keep the end of the cut square. Use the utility knife to remove any burrs or rough edges on the PVC conduit.

Prime one end of the PVC electrical conduit and the fitting at the box. When the primer is dry, apply a thin coat of PVC solvent cement to both the conduit and the fitting and push the pipe into the fitting. Hold the pipe in place for a few seconds to give the cement time to hold.

Repeat the process at the other end. You may need to spring the PVC conduit a bit to get it started into the fitting. The PVC electrical conduit should fit tightly with no noticeable bends or sagging of the conduit if you measured correctly. If the run is particularly long, install PVC conduit support brackets along the length of the PVC conduit.

Step 5: Pull the Wiring Through the Conduit.

For short runs bundling the wires and taping the end may allow you to push the wire bundle through the conduit to the electrical box at the other end.

On longer conduit runs, threading a fish tape through the conduit run is preferable. With the tape in the conduit, you can attach the wire bundle to the end of the fish tape and pull the entire set of wires through the conduit. Leave plenty of wire outside the box to make attaching switches and outlets to the wires.

At this point, you are ready to make your connections, install switches and outlets, and add the cover plates to the electrical boxes.

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PVC Schedule 40 or Schedule 80

In most instances, schedule 40 PVC electrical conduit is suitable for most residential electrical applications. If your wiring systems expose the PVC conduit to high hazard or traffic areas where the PVC conduit might suffer bumps, impacts, or other threats, the heavier wall schedule 80 PVC conduit is a better choice.

Your local building code is a good reference for using schedule 80 or schedule 40 PVC conduit. If in doubt, consult with a licensed electrician or your local building inspections officials.

Dennis Howard
Dennis Howard

Dennis is a retired firefighter with an extensive background in construction, home improvement, and remodeling. He worked in the trades part-time while serving as an active firefighter. On his retirement, he started a remodeling and home repair business, which he ran for several years.

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