Conduit is piping or tubing designed to enclose and protect the wires that distribute power throughout your home. Conduit comes in both rigid and flexible forms and is made from a variety of materials for use in different applications. In homes, conduit is most often used for protecting outdoor or exposed wires or cables, such as those in an unfinished basement or garage. In some instances, wiring may be run across a wall’s surface, secured behind a protective covering called raceway, which is similar to conduit.
Local building and electrical codes regulate the type of conduit that can be used in specific applications and how it must be installed. Check with your local building inspector before beginning a project and be sure to obtain any required permits. When your work is complete, always have it inspected for compliance with local codes and to ensure that it has been safely installed. Unless you are an experienced electrician, it may be best to consult a professional before beginning any electrical work.
Factors to Consider
• Metallic Conduit—Rigid, flexible, tips for use
• Nonmetallic Conduit—Rigid, flexible, tips for use
Rigid metallic conduit is most often used in commercial applications, but it can be a smart choice for straight runs of wire or cable through an attic, garage, basement or crawlspace, as it protects against nicks, punctures or cuts to wiring, including nicks made by animals that may chew on exposed wiring.
Rigid metallic conduit includes:
• Electrical metallic tubing (EMT), which is lightweight and easy to install.
• Intermediate metallic conduit (IMC), which has a thicker galvanized wall, making it suitable for
• Galvanized rigid conduit (GRC), which is thickest and offers the most protection for the wires inside,
but is more expensive and requires threaded fittings.
The wide availability of elbows, couplings and other fittings make the joining of rigid electrical conduit easier than ever for homeowners.
Flexible metallic conduit bends and twists easily, allowing turns at corners without the use of separate elbow joints. It is often used where rigid conduit is difficult to install or to connect permanently wired appliances, such as a water heater.
Prewired conduit, or armored cable, offers an all-in-one solution with the wires already run through the flexible conduit.
Tips for Using Metallic Conduit
• With all metallic conduit, file off the rough edges to prevent damage to wires as they are pulled through the conduit.
• Metal electrical boxes must be used with metallic conduit.
• Running a green grounding wire is recommended, though code may allow the metal conduit itself to serve as the grounding conductor.
Generally made of PVC, rigid nonmetallic conduit is a good choice for outdoor residential applications, such as wiring landscape lighting or burying cables. PVC doesn’t rust and the pieces are glued together with PVC cement making connections watertight. Always run a grounding wire when using PVC conduit, and check local electrical codes to ensure compliance.
Flexible nonmetallic conduit is a useful solution where running rigid conduit is difficult.
• Blue electrical nonmetallic tubing (ENT) is for indoor use only. PVC rigid fittings can be used with ENT
inside walls, floors and some ceilings or encased in concrete.
• Outdoor flexible nonmetallic tubing is strong and watertight. Often known as liquidtight, it is
non-corrosive and weighs less than flexible metallic tubing, making it a good choice for applications such
as heating and air conditioning and outdoor lighting.
Tips for Using Nonmetallic Conduit
• Nonmetallic electrical conduit can be used with metal or plastic boxes.
• Always run a grounding wire when using PVC conduit.
• Some local codes require the use of metal conduit outside. Check the codes for your area before doing any electrical work.
The table below lists the most common types of residential conduit and their applications.