How to Repair an Underground Electrical Wire Break

Three colored cables inside of red conduit, ready to be buried.
  • 8 hours
  • Intermediate
  • 250
What You'll Need
Electronic monitoring equipment
Junction box
Waterproof electrical connectors
Several lengths of wires for splices
Wire cutters
Wire stripper
Heat gun

Sometimes things can go wrong with buried outdoor cables, especially when lawn tools are involved. When it turns out that something has cut one or your underground wires, you can use a splice kit to fix it. All you need to do is follow a few simple steps and use a few key pieces of equipment for a proper solution.

Step 1 - Purchase Electronic Monitoring Equipment

If you don’t know the location of the break, you can purchase electronic locating equipment at most electrical supply houses or big box stores. These tools will require some basic knowledge of electrical circuitry and a little patience as well.

Step 2 - Call the Phone and Utility Companies

Another alternative is to phone your local electric company and use their locating service. Most provide this service for free when locating the main power wires running from their incoming source to your meter or box. Locating other underground wires for light poles, barns, pools, garage, etc. may incur a small fee; the best practice is to call and ask.

Step 3 - Dig up the Affected Wire

First and most importantly, make sure you turn main electrical supply off before digging or attempting any repair to, or addition to, the electrical wire underground. Use a non-contact voltage tester afterward to confirm that the cable is no longer live. Then, dig along the sight path between the electric cables exit and entry points.

Step 4 - Purchase Junction Boxes and Cable Connectors

If you are going to add additional circuitry to your existing wire underground, purchase waterproof junction boxes where connections can be made inside the box. This will protect the connections from corroding due to moisture and chemical elements from the surrounding ground.

Special sealing box cable connectors provide the waterproof seal for the electrical wiring that enters the box as well. These are a must when joining wires together in the watertight box. They have silicone inside the connector which will seal out the moisture after you have inserted the wiring. Do not reuse these once you remove them, however, because you may strip away too much of the silicone when you pull it off, and it will no longer be watertight if reused.

Step 5 - Use a Splice Kit

A splice kit containing an inline connector will join the two ends of a break securely in a polyolefin sleeve, which will shrink when heat is applied, to maintain a water-resistant connection. Inside the heat shrinkable tubing is an adhesive liner that will melt when heated. This will coat the connection and cover the wire with adhesive, oozing out the ends of the tubing as it shrinks. This method can be used if wiring is deep in the ground and no possible damage from gardening tools hitting it.

A better choice for wires that you fear might get cut again will be connectors with a thick protective covering on them and silicone-based sealer inside for waterproofing.

Before you use the splice kit, you will need to cut the damaged wiring on either side of the break, and strip the outer sheathing back about three inches. Then, insert each conductor into the connector and match the colors. Tighten the screws in the connector, and heat the shrink tube with a heat gun to complete the seal.