Conduit provides a secure barrier between electrical wiring and exterior conditions that could damage or corrode it over time. A wide variety of conduit is available for both interior and exterior applications, including flexible conduit that allows wires to curve around obstacles. However, rewiring these conduits during repairs and renovations can be challenging. With conduit sometimes running hundreds of feet long, it can be difficult to ensure that wiring runs all the way through without getting caught. Fortunately, there are several methods to pull wire through conduit, and some of the best are covered here.
Cable Pulling Methods
In ideal situations, you’ll work with a conduit that still has old wire running through it. In these cases, you can simply attach the end of the old wire to the end of the new wire and use it as a pull wire, pulling the new line through the conduit. However, this is not always an option, especially when working with new conduit or severely damaged old wiring.
If you find yourself needing to pull wire through conduit, you can choose from multiple methods. Some of the best methods for pulling wire through electrical conduit are listed below, along with their advantages and limitations.
1. String Method
The string method is the simplest technique for pulling wire through conduit and relies on a strong string called a pull string. The method works as follows:
- Tie the string: Tie a strong string to a long, inflexible rod.
- Push the rod: Push the rod through the conduit, tied end first. Continue pushing until the string emerges from the opposite side of the condit.
- Attach the wire: Tie the electrical wires to the string.
- Pull the wire: Pull the rod and string through the conduit, pulling the wire along with them.
This method works best on pieces of conduit that are short and straight. Longer pieces of conduit or lengths with more curvature will require an alternative method.
2. Conduit Mouse Method
The mouse method is a variation of the string method that uses a tool called a conduit mouse or conduit piston instead of a rod. This tool is a small foam cylinder that is slightly smaller in diameter than the interior of the conduit. It is used in tandem with a shop vacuum. The method for using this tool is detailed below:
- Tie the string: Take the conduit mouse and tie a strong, light string to it. There should be a wire loop running through the mouse for this purpose.
- Insert the mouse: Place the mouse into the conduit opposite from the side you plan to pull from. Fit the mouse so that it fills the conduit space and so that the string follows behind it.
- Apply the vacuum: Take the shop vacuum and apply it to the opposite end of the conduit. Make sure that the vacuum hose is fitted to the conduit so that it creates the best suction.
- Pull the mouse: Turn on the vacuum and apply it until the mouse is sucked to the end of the conduit. Turn off the vacuum and remove the mouse.
- Attach the wire: Untie the string from the wire loop on the mouse and secure it to the wire.
- Pull the wire: Pull the opposite end of the string to pull the wire into the conduit. For longer conduits, have a partner feed the wire into the conduit.
This method is very useful for conduit with more complex twists and turns but can be limited by the length of the conduit.
3. Fishing Weight Method
The fishing weight method uses a heavy fishing weight to guide wiring directly through a conduit. The method works as follows:
- Tie the weight: Tie a heavy fishing weight to the end of the wires using string or fishing wire to give the weight a 2- to 3-inch lead in front of the wiring. Be sure to choose a fishing weight that is thin enough to run through the conduit but heavy enough to pull lubricated wire.
- Insert the weight: Place the fishing weight inside the conduit and adjust the placement of the wiring so that it can easily move behind the weight.
- Drop the weight: Drop the fishing weight into the conduit. If you are working with a free-moving length of conduit, lift the end of the conduit higher than the weight so that gravity can pull the weight along. When necessary, adjust the conduit orientation to get the weight around curves in the conduit. Continue this process until all the wire has been pulled through the conduit.
This method is somewhat limited in its applicability. It works best for straight, vertically-run conduit, though it can be applied to almost any conduit that is free to move around. It is not ideal for a conduit that is fixed in a horizontal position or has excessive curves.
4. Fish Tape Method
The above methods are excellent for straight conduits but are much more difficult for pulling through conduits with more curvature. So how do you pull wire through flexible conduit with multiple turns? The fish tape method is the most common solution. This technique uses fish tape, a tool commonly used by electricians for pulling wire. Fish tape is a long, flat metal wire wound inside a spool with a hook at the end. To use fish tape, you’ll also need wire strippers and linesman pliers. The fish tape method works as follows:
- Feed the tape: Feed the end of the tape into the end of the conduit you wish to pull from. Continue pushing the tape through the conduit and unwind the spool as you go. When the end of the fish tape emerges from the end of the conduit, stop feeding the tape.
- Strip insulation: Strip insulation from the end of the wire using wire strippers. If you are feeding multiple wires, strip each wire a different amount, leaving one wire longer than the others.
- Attach the wires: Hold the wires together so that the insulation is aligned and twist them together with pliers. Bend the longest wire so that it forms a hook and attach it to the hook on the end of the fish tape. Once these are attached, wrap the attachment point with electrical tape to ensure that they don’t detach during the pull process.
- Pull the wires: Pull the wire into the conduit by pulling the fish tape while a partner feeds the wire.
The fish tape method can be applied to nearly all types of conduit. Note that fish tape is available in a range of lengths from 25 feet to 100 feet, so be sure to get one appropriate for your application. For shorter lengths or small jobs, nylon tape is an economical option that works just as well.
5. Joint Fish Tape Method
In some cases you may encounter conduit with 90 degree turns or existing wires — both of these can prove problematic.
Pulling wire through conduit with existing wires is difficult because any technique you use may get caught on the existing wires — the conduit mouse and fishing weight method are completely unuseable in these cases for this reason.
Pulling cable through conduit bends can also prove problematic. For most conduit, the more severe the angle, the more difficult it is to get a pull string or fish tape in place. This problem is even more pronounced with PVC conduit, as the angle joints can easily catch fish tape as it works through the conduit.
One method to get around these problems uses two fish tapes run at each end of the conduit. Note that this method does require working with a partner. The method goes as follows:
- Create loops: Take one of the fish tapes and expose the end. Use strong string to create a bundle of loops around the end of the fish tape and firmly attach it using electrical tape.
- Create a hook: Take the second fish tape and make a hook at the end of it. Test the two ends to make sure that they can easily catch on one another.
- Feed the tapes: Have you and your partner stand at the two ends of the conduit, each with one of the two modified fish tapes. Begin to feed the tapes at each end. Plan it so that your tapes meet at the problem point in the conduit.
- Hook and pull: When the tapes meet, spin the hooked end so that it is more likely to grab one of the loops. Once you think you have caught the other line, tug to test. When the two lines are attached, pull one end of the fish tape to pull the other all the way through the conduit.
Once you’ve caught and pulled one fish tape through the entire conduit, you can continue with the normal fish tape technique for pulling wires through. It’s important to note that conduit with severe turns or existing wires will require thorough lubrication to get the wires all the way through without catching.
Additional Tips for Pulling Cable
Before you pick one of the above techniques for pulling wire through conduit, it is important to analyze your conditions and adequately prepare for the process. Some essential tips include the following:
- Look for existing tools: While examining your conduit, check for any existing wires or cables in the conduit, as these can be used as pull strings for the new wiring. Also, check to see if these wires are intact — broken wires can pose obstacles during the wire pulling process.
- Check local codes: Sheathed cables are an alternative to insulated wiring and are permitted by the National Electrical Code. However, they aren’t universally allowed to be used in interior conduits and should never be used in outdoor applications. Even if they are allowed, the size of the sheathed cable makes it nearly impossible to run it through anything other than short, straight conduits. If you are thinking about rewiring with non-metallic cable, be sure to check local laws and codes to make sure this is acceptable and ensure that your application will be compatible.
- Lubricate the wiring: Pulling wires is difficult enough when working with straight conduit. However, bends and turns increase friction on the wire, making pulling more difficult. If your conduit has bends and curves, lubricate your wiring with a non-conductive lubricant as you feed it into the conduit. This gel or soap substance coats the wiring, making it slick enough to slide through the conduit more easily. Apply the lubricant directly to the wire before pulling it through, using less toward the end of the pull. As with any lubricant, follow the manufacturer’s instructions for optimal functionality.
- Work with a partner: While you can theoretically pull wire yourself, it is best to work with at least one other person, no matter what method you choose. This person can help by pulling the wiring while you add lubricant or vice versa. This is especially recommended for longer and more complicated runs of conduit.
- Examine your conduit: By far the most important preparation tip is to inspect the length of your conduit from end to end. Measure the length of the conduit and make note of any curves that may pose problems. Be sure that whatever method you decide to use is appropriate for the length and shape of the conduit in question. Also take note of the type of conduit you are running — conduit with corrugated edges will catch wires more easily across the length of the conduit, while smooth PVC conduit may only catch at joints.
Types of Conduit
One of the important things to consider when preparing to pull cable is the type of conduit you’ll be working with. The thickness of the conduit, as well as the texture, will help determine the best method for pulling wire through the conduit. Thinner conduits may not allow for the use of fishing weights or conduit mice, while larger conduits may support these methods.
Some common types of conduit include the following:
- Divisible conduits
- Fiber optic conduits
- Jumbo conduits
- Metallic braided conduits
- Plastic conduits
- Polyamide conduits
- Retrofittable conduits
- Specialty polymer conduits
Whatever type of conduit you’re working with, AerosUSA can provide high-quality versions at excellent prices.
About AerosUSA Conduits
AerosUSA is a leading supplier of high-performance conduit systems for industrial applications. As the exclusive U.S. representative of world-renowned manufacturer Flexa GmbH, we carry an extensive and exclusive inventory of high-quality conduits.
Of particular note are our polyamide conduits and galvanized conduits, made to fit the needs of various industries. Our corrugated polyamide conduits provide excellent impact and UV protection and feature snap-on connectors that are easy to use. Our metallic galvanized conduits, on the other hand, provide corrosion protection and shielding needed for the most demanding industrial environments.
Regardless of the conduit type you need, AerosUSA provides conduits that offer:
- Cable protection
- Excellent seals
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- High impact resistance
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We also supply other cable protection and management systems. Our extensive line of quality Flexa GmbH protection products includes:
- Cable glands
- Cable management accessories
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With our extensive inventory, competitive pricing and fast deliveries, you can trust us to have the solutions you need. On top of it all, we staff knowledgeable personnel with the industry experience needed to pair our customers with the right solution, regardless of their industry. We’ve served many industries, including:
- General machine
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We can assist your company too. Contact us today to see how AerosUSA can help.