Fishing Electrical Wire Through Walls

A decent stud finder is a must-have for every wire-fishing job, but don’t throw it back in your pouch after you’ve located the studs. Use your stud finder to check the whole wall cavity for obstacles like blocking and abandoned headers. You don’t want to find out the hard way that you should have fished your wire one stud cavity to the left or right. “If there’s an existing outlet, you can also open it up and fish wire up through the opening to check for blocking in that bay,” Cross says.

Flex bits and glow rods are the go-to tools pros use for fishing wires. Flex bits are great for drilling holes in hard-to-reach spaces (see “Invest in a Bumper Ball,” below). The two most common lengths are 5 ft. and 6 ft., but extensions are also available. A 3/4-in. x 54-in. flex bit costs about $50 at home centers. Buy a bit that has a hole on the end of it so you can use the bit itself to pull wires. Once your hole is drilled, you can shove a glow rod through the hole to start fishing wire, attach your wire to the eyelet at the end and pull it back through.

Glow rods can also be used to hook wires to pull them out as a wire snake tool. As their name suggests, glow rods glow in the dark. This makes them easier to spot when you’re working in dark areas fishing wire (which is most of the time). Glow rods come in various lengths and thicknesses, and you can combine as many sections as the job requires. Thinner rods flex more and work better when you have to make sharp turns when fishing wire. A thicker rod can span longer distances and is better for hooking wires that are more than a few feet away. A 9-ft. glow rod kit costs about $40 at home centers. Expect to pay about $60 for a 24-ft. kit. Don’t forget an electrical tester.

When fishing wire to pull it toward you, make sure there’s more than enough wire to hook on to. Sometimes, it’s a real challenge to grab hold of a wire, and once you have it hooked, you don’t want to lose it. Always makes sure that you have at least 5 or 6 ft. of extra wire to keep up the tension on the hook the whole time you’re pulling on it.

Sometimes, you don’t need to use glow rods at all when fishing wire. Most flex bits have holes in the ends of them, perfect for fishing wire. If you have access to where the flex bit pops out, attach your wire directly to the bit and fish the wire through that way. Twist the wire and tape it up to make sure it doesn’t come off when you’re pulling it back through. Remove your bit from your drill before pulling so you don’t accidentally spin the bit and twist up your wire.

When you’re installing new recessed can lighting, fishing wires from one light to another is easy because you have a great big hole to pull the wires through. But even if you’re not installing new lighting, you can use the existing openings. Many cans can be easily popped out of the opening by removing a few screws. “Be extra careful fishing wires through ceilings, ” Cross says. “Take a good look around, because there could always be existing wires or plumbing in ceilings.”

Mud rings, also called drywall brackets or low-voltage “old-work” brackets, are great for protecting the drywall when you’re drilling with a flex bit or cranking on a glow rod. They’re easy to install (just tighten two screws) and inexpensive. Once the wires are connected, you can screw the wall plate to the mud ring. Mud rings are approved only for low-voltage wires like communication and coaxial cables. If you need to install a regular gang box for an electrical receptacle or wall switch, install the mud ring temporarily to protect the drywall while you fish the wire, then remove it. Check out nine more tips for DIY electrical wiring.

Additional outlets above the counter space—that’s one of the most popular electrical retrofits. Electricians loves these jobs because they can just fish wire through a flexible conduit installed right through the base cabinets. If you drill the holes for the conduit as far back and as high as you can, no one will ever notice.

Wires aren’t supposed to be installed any closer than 1-1/4 in. from a penetrable surface (the outside of the drywall). That means you shouldn’t be drilling holes right next to the drywall. But it’s not always easy to control where a flex bit goes. A Bumper Ball flexible drill bit guide installed on the end of your flex bit will help maintain the proper space between the bit and the outside of the wall cavity. You can buy a set of two at electrical suppliers or at licensedelectrician.com.

When you hook cable to the eyelet of a glow rod, strip the plastic sheathing back about 6 in., then cut off the hot and neutral wires. Then, wrap the remaining ground wire through the rod’s eyelet and wrap it back around the wire’s sheathing several times. Finally, wrap the whole area with electrical tape. When hooking coaxial cable, just tape the whole wire to the glow rod. You’ll never lose a light wire just using tape. Use the same technique when working with communication cable like phone wire. If you try to hook one of the small communication wires, you could stretch and damage that individual wire several feet down inside the sheathing.

You know your wire is in there somewhere, but you just can’t seem to find it. It’s probably hung up on another wire or pipe, but guessing isn’t going to solve the problem. Instead, shine a flashlight onto an inspection mirror to find out exactly what’s going on. This is a simple, inexpensive tip that can save you a lot of time and frustration. Pick up an inspection mirror at an auto parts store for less than $10. Or bump it up a notch and pay a few more bucks for a mirror with small built-in lights, so you can see exactly what’s going on.

The best advice for fishing wires through insulation is “Avoid it if you can.” The potential is always there to damage the vapor barrier or bunch up insulation, leaving cold spots in the wall. If you must fish wires through exterior walls, the best tip is to avoid spinning the flex bit until you make solid contact with the wood you plan to drill through. If you drill too early, you’ll end up creating a large insulation cotton candy cone, which will make retrieving your bit difficult, if not impossible.

It’s really tempting to fish low-voltage wires (like coax and Cat-5e) through existing holes occupied by electrical cables, but don’t do it! Even though cables are insulated, the high-voltage current can interfere with the signal in the low-voltage wires. This could result in bad TV reception or unreliable phone and Internet service. Drill a new hole, and keep the new low-voltage wire several inches away from electrical cables. It’s OK to run low-voltage wires perpendicular to cables, and it’s also OK to run low-voltage wires next to electrical wires that are encased in conduit or metal sheathing.

Have plenty of extra wire or cable on hand, because it’s not likely that you’ll be able to fish a wire in a straight line from Point A to Point B. There’s also the possibility that your wire might get hung up on something, and you’d have to abandon it and start over. “I’m a big fan of more wire than less,” Cross says. “I’d rather look at it than look for it, and it’s a lot cheaper to pull a little extra than to redo it.” He likes to leave between 12 to 24 inches of extra wire at each end.

If you’re installing more than one wire, save yourself a lot of headaches by identifying the wires as you install them. It’s a lot harder to figure out which wires go where when they’re covered with drywall. The electricians we talked to use a “code” for marking wires, and so can you. Develop a system and write it down. You don’t want to have to guess after you’ve gone through all the trouble of running the wires all around the house.

About the Expert

• Matt Cross is a licensed electrician in the State of Massachusetts. He has over ten years of industry experience in residential and commercial work.