How to Run a Phone Cable Underground

Written by gloria hutson
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How to Run a Phone Cable Underground
Underground phone cables enable homeowners to add additional lines to other outbuildings on the property. (telefono antiguo image by Juan David Ferrando from

If you decide to run a phone cable underground to another building from your phone's outside service box, doing the work yourself can save money. The trench for outdoor telephone cables is usually shallow and narrow, requiring only enough depth to cover the cable. To hide unsightly wiring, secure the cable running up the outside wall of your house or building with a short piece of PVC pipe.

Skill level:

Things you need

  • Indoor/Outdoor telephone cable
  • Tape measure
  • Trench digger or shovel
  • PVC pipe, 1 1/2 inch
  • 2 90-degree PVC elbow fittings
  • Drill
  • Galvanised pipe clamps, 1 1/2 inch, and screws
  • Screwdriver

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  1. 1

    Measure the ground distance between the outside service box and the point of the new connection. Calculate this distance with the length of cable you need to connect each junction box. Include any outside and indoor wall or floor space the phone line will travel when calculating cable length.

  2. 2

    Dig a trench, using a trench digger or shovel, 4 inches to 6 inches deep and the distance between each connection.

  3. 3

    Place the PVC pipe vertically under the service box. Determine the pipe's length by measuring the distance between the bottom of the service box and the trench floor. Connect an elbow at the bottom of the pipe aligned with the trench opening. Repeat this process at the new point of connection.

  4. 4

    Run the phone cable along the trench and up through the vertical PVC pipes and fittings. Wire the phone cable connections.

  5. 5

    Secure the vertical pipes to the outside walls using galvanised pipe clips and screws.

Tips and warnings

  • Measure the total inside and outside distance between connections. Calculate how much phone cable length you will need to finish the job without having to splice the wiring.

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