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• Tips for installing & inspecting electrical conduit in homes
• Electrical conduit cutting, bending, installing suggestions
• Guide to Electrical Hazards in Buildings: inspection, detection, & repair advice

This article answers basic questions about installing electrical conduit. Electrical conduit is metal or plastic rigid or flexible tubing used to route electrical wires in a building. Electrical conduit for wiring has some advantages in protecting wires and also in running multiple wires to a location. But the proper selection of electrical conduit materials, fittings, and installation are important for safe electrical wiring. Readers of this article should also see Electrical Code Basics and SAFETY FOR ELECTRICAL INSPECTORS. This website provides information about a variety of electrical hazards in buildings, with articles focused on the inspection, detection, and reporting of electrical hazards and on proper electrical repair methods for unsafe electrical conditions. Critique and content suggestions are invited. Page top photo courtesy of Tim Hemm.

Credit is given to content editors and contributors. © Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. Sketch at page top courtesy of Carson Dunlop.

Safety Warning: Do not attempt to work on your electrical wiring, switches, or outlets unless you are properly trained and equipped to do so. Electrical components in a building can easily cause an electrical shock, burn, or even death. Even when a hot line switch is off, one terminal on the switch is still connected to the power source. Before doing any work on the switch, the power source must be turned off by set­ting a circuit breaker to OFF or removing a fuse. See SAFETY FOR ELECTRICAL INSPECTORS and Electrical Wiring Books & Guides

Electrical Conduit Installation Tips for Homeowners & DIY Repairs

Elizabeth Sluder

Cutting, Bending and Threading Electrical Conduit

Electrical conduit is often used to hold and protect house wiring. In some localities electrical conduit is required by the local code. Conduit protects building wiring from damage better than flexible steel (BX) cabling or plastic sheathing (Non metallic sheathed or NMC wire). However, it electrical conduit is more difficult to install and it requires both some special tools and some special knowledge about permitted bending radii and similar details.

There are four types of electrical conduit available

• Thin-wall metal conduit
• Rigid threaded conduit
• Plastic conduit
• Flexible metal conduit (for special applications such as shown at left sketch, but steps must be taken to prevent water from entering the conduit and/or special water-resistant wiring and fittings are required)

The most common type of electrical conduit for house wiring is the thin-wall type. Thin-wall conduit is too thin for threaded joints. It is joined to other lengths of conduit and to boxes by pressure-type fittings. Thin-wall conduit is sold in ten-foot lengths in either one-half inch or three-quarter inch (outside) diameter.

The one-half inch conduit can contain four No. 14 wires or three No. 12 wires. Three-quarter inch conduit accommodates four No. 10 or five No. 12 wires. These capacities are for wires, not pairs. The wires used are the same as the individual conductors found in steel armor cable and plastic sheathed cable. Wires in conduit must follow standard coding. In a two-wire electrical circuit you need one black wire, one white wire, and one ground wire.

The general procedure for using thin wall conduit is similar to the use of steel armor cable. The big difference is that conduit cannot be "snaked" through openings in ceilings and walls. You must have full access to joists and studs to install electrical conduit. So you probably won't want to use it unless your local code requires it

What tools you need and the procedures for using conduit?

Tools for Cutting Electrical Conduit

Thin-wall conduit can be cut with a special electrical conduit cutter. To use the cutter, clamp it around the conduit. To cut the conduit, tighten the knurled nut in the handle. As you tighten, force the cutter around the conduit. The sharp cutting blade cuts a groove that deepens with each revolution, making a smooth, quick cut. After cutting through the conduit, file off any burrs around the edge of the cut.

Tools for Bending Electrical Conduit

Thin-wall electrical conduit can be readily bent by using a special tool designed to make a smooth, even bend with little effort. The more bends in a run of conduit, the more it is to “fish” the wires through.  Plan the conduit run carefully to avoid sharp bends and to make as few bends as possible.  Never have more than four right angle bends between openings.  Follow the manufacturer’s instructions for the type of conduit bender you use. 

How an electrical conduit bender works

Screw a 30-inch length of threaded pipe into the bender head (sometimes called a an electricians “hickey.”)

Insert the conduit into the bender through the hook at the top of the head. The hook marks where the bend will start.

Put one foot on the conduit near the head and lever the pipe handle backward, checking the angle of the bend as you go.

How to thread electrical wires through conduit

A fish tape is a thin, flexible metal tape with a hook on one end. The tape is usually packaged on some type of reel. The tape is used to pull wires through conduit or through openings in walls. For conduit use, the tape is inserted in one conduit opening and worked through to the next opening. The wires to be drawn through the conduit are bent around the hook on the fish tape.

If the run is long and has a few bends it is a good idea to wrap some electrical tape around the wires to hold them on the hook.  The tape is then reeled in to draw the wires through the conduit.  A slow, steady is less likely to kink the tape or jam the wires than is a series of sharp.

Electrical codes allow multiple electrical wires to be pulled through a single conduit, but limit the number of wires allowed in a conduit run depending on the number of wires and the wire diameter or gauge.  The more wires you pull, the more crowded the conduit, so buy larger conduit---perhaps 3/4 inch instead of 1/2 inch.

What are some Typical Defects we can See when Inspecting Electrical Conduit Wiring?

If our inspection is limited to an external, visual inspection of electrical conduit, we may not immediately be able to see safety and electrical code violations such as use of improper wire type or too many wires in a conduit, but here are some easy to spot concerns that merit further review by an expert:

Damaged electrical conduit. While electrical conduit can provide superior protection for electrical wiring, rigid conduit is also vulnerable to impact damage. We often see a free-standing electrical junction box, perhaps holding an electrical receptacle, which has been struck and broken off. Look for conduit which has been bent, dented, crimped, cut, or broken. Tim Hemm's photo at left shows how easily a rigid conduit mounted outdoor electrical receptacle can be kicked over and broken. This condition adds the risk of a nicked or cut wire insulation making an immediate risk of electric shock or electrocution.

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• Elizabeth Sluder, Montross, VA, the original author of this article, is a public school teacher who writes basic educational articles about a variety of building, construction, and other topics. Her husband, a licensed electrician, consults for her writing on electrical topics. Her articles appearing at the InspectAPedia ^TM Website have been edited, illustrated, and on occasion content has been added by the website author. These articles are © 2009 InspectAPedia copyright-protected, all rights reserved.
• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• Timothy Hemm has provided photographs of various electrical defects used at the InspectAPedia ^TM Website. Mr. Hemm is a professional electrical inspector in Yucala, CA.
• NFPA - the National Fire Protection Association can be found online at www.nfpa.org
• The 2008 NEC National Electrical Code (ISBN 978-0877657903) Online Access LINK (you'll need to sign in as a professional or as a visitor)

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