• Share:
Fix Underground Wiring

Accidentally cut an underground electrical wire? The easiest way to repair it is with an underground splice kit, which uses a rustproof connector to repair and seal the break.

By the DIY experts of The Family Handyman Magazine

Assess the damage

If you’re digging holes in your backyard, you should always call 811 a few days beforehand to mark all the underground utilities. Unfortunately, privately owned wiring will not be marked, so it’s still possible to strike an electrical cable. It’s especially likely if you’re digging between the house and a freestanding garage, shed or yard light. If you do cut a power line, though, it’s easy to fix. Here’s how.

First turn off power to the electrical device fed by the broken cable at the circuit panel. Then dig 12 in. on each side of the break in the wire and gingerly work your way to the cable. You’ll find the cable anywhere between 12 and 24 in. deep. When you locate the cable, use a noncontact voltage detector to ensure there’s no power.

If you have a broken underground line and no clue where the break is, hire an electrician with an underground open/short locator. The electrician will be able to locate and mark the underground cable, determine how deep the cable is buried and pinpoint within a few inches where the problem exists.

<p>Heat-shrinkable tubing splice</p>

Heat-shrinkable tubing splice

<p>Gel-filled plastic shield splice</p>

Gel-filled plastic shield splice

Two Splice Kits

Underground AC splice kits come in two varieties: heat-shrinkable tubing and gel-filled shield. Both use a brass splicing block to connect the wires. But they differ in how they protect the splice.

The most common type of kit protects the splice with an 8-in. length of heat-shrinkable tubing filled with watertight hot-melt adhesive. (The Gardner Bender HST-1300, available through our affiliation with Amazon.com, is shown here). Slide the tubing over the cable before you connect the wires to the splice block. Then slide the tubing over the connector and shrink it with a heat gun (best) or a torch (gently!). The other type is a corrugated plastic shield filled with an encapsulating gel. (The Tyco Electronics PowerGel WrapAround UF Splice Kit, also available through Amazon.com, is one brand). It’s twice the price, but it installs much faster, is goof-proof and is very long lasting.

Heat-shrinkable tubing repair

Replace the whole section of cable that you dug up with the same gauge UF (underground feeder) cable. Cut the cable about 12 in. on either side of the break. Then strip back the sheathing 2 in. and the wire insulation 5/8 in. Use two special underground splice kits (sold at home centers) to connect the new cable section. Slide the heat shrink tube over one end of the cable, then connect the wires to the brass connector (Photo 1). Do this on both ends of the new cable. Once the damaged cable is replaced and the wires are joined with connectors, slide the heat-shrink tube over each connector (Photo 2). Heat the tube with a heat gun until it shrinks tight on the connector and sealant bubbles out the end.

Gel-filled splice kit repair

Start by cutting out the damaged sections. Then cut, separate and strip the ends of the buried cable (Photo 1). Do the same for the additional section of cable (if needed). Next, secure the wires in the brass holder (Photo 2). Locate the splice block in the protective shield (Photo 3). Wrap the shield around the splice and secure it (Photo 4). Then repower the circuit to make sure the splice works.

To make it easier to locate the splice in the future, mark it with bright-colored surveyor’s tape (Photo 5). Then refill the hole.

<p>Low-voltage cable splices</p>

Low-voltage cable splices

Splicing Low-Voltage Cable

Besides underground power cable, it’s also possible to slice through low-voltage lighting, irrigation and telephone cable and coaxial cable. Since they’re low voltage, you may be tempted to just twist the wires and wrap the splice with electrical tape. It won’t work. Instead, head to a home center and get a couple of low-voltage connectors for direct burial. They rely on gel to encapsulate the splice to prevent water intrusion and corrosion.

For low-voltage stranded cable, like you might find on lighting, use the wire nut/gel-filled tube style. Twist on the wire nut, plunge the connector into the tube until the gel oozes out the top, then snap the lid. For solid irrigation and telephone wire, shove the wires in an insulation piercing gel-filled connector and snap it closed.

Back to Top

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • 4-in-1 screwdriver
    • Lineman's pliers
    • Spade
    • Non-contact voltage tester
    • Utility knife
    • Wire stripper/cutter

You'll also need a heat gun for the heat-shrinkable tubing.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

    • UF cable
    • Heat-shrinkable underground splice kit or Gel-filled wrap-around splice kit
    • Surveyor’s tape

Comments from DIY Community Members

Share what's on your mind and see what other DIYers are thinking about.

1 - 1 of 1 comments
Show per page: 20   All

October 17, 7:54 PM [GMT -5]

Always be sure there are NO pin holes or torn places in the heat shrink. I strongly advise adding a non-conductive sealant in the splice (designed for the voltage/current of the wires). Any "leakage" of electricity will cause troubles in the future and will result in corrosion of the splice. I also advise having some way to find the splice(s) in the future. Some people place short pieces of pvc pipe next to the splices and a flush sprinkler casing (or similar item) as we tend to forget. That's why pirates made treasure maps.

+ Add Your Comment
closeX

Add Your Comment

Fix Underground Wiring

Please add your comment
closeX

Log in to My Account

Log in to enjoy membership benefits from The Family Handyman.

  • Forgot your password?
Don’t have an account yet?

Sign up today for FREE and become part of The Family Handyman community of DIYers.

Member benefits:

  • Get a FREE Traditional Bookcase Project Plan
  • Sign up for FREE DIY newsletters
  • Save projects to your project binder
  • Ask and answer questions in our DIY Forums
  • Share comments on DIY Projects and more!
Join Us Today
closeX

Report Abuse

Subject
Reasons for reporting post

Free OnSite Newsletter

Get timely DIY projects for your home and yard, plus a dream project for your wish list!

Follow Us