How to bury electrical wire

Written by henri bauholz
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How to bury electrical wire
Run buried wiring through a plastic pipe. (balticboy/iStock/Getty Images)

Sometimes electrical wire needs to be run from the main building to an outlying area such as a work shed, studio or a lamp post. The best solution is usually to run the wires underground to the place that needs the electricity. This can be done safely and at a reasonable cost and is much safer than placing the electric wires above ground.

Skill level:

Things you need

  • Shovel
  • Pick
  • Hoe
  • 3.7 cm (1 1/2 inch) PVC plastic pipe
  • PVC couplings (straight and 90 degree)
  • PVC pipe caps
  • PVC cement
  • Outdoor wire (12/3 UL)
  • Wire cutters
  • Electric drill
  • 1.8 cm (3/4 inch) drill bit

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  1. 1

    Install an electrical box at each end of the outdoor run. One box will go just inside the main building and the other will go on the inside of the outdoor structure (a lamp post has its own built-in electrical box). Check with the electrician, who is doing the electrical work, to make sure the location of each box is correct.

  2. 2

    Dig a trench that is at least 30 cm (1 foot) deep and runs in a straight line from the main building to the outside location. Place all the soil next to to trench in neat piles. Make sure the trench comes up to the edge of the building at a point that is right below the electrical box that will receive the wire.

  3. 3

    Lay out the PVC pipe in the bottom of the trench with a straight coupling placed between each length of pipe.

  4. 4

    Run the wire through the pipe and the coupling joints. Use 12-gauge three strand underground cable (the label will read, 12/3 UL). You can buy the wire by the spool, so that the distance is covered by a single piece of wire. The wire should continue upwards into the box with at least 30 cm (1 foot) left over at each end so the electrician has plenty of wire to work with. Leave the wire loose for the time being.

  5. 5

    Connect all the pieces of PVC pipe together by coating both ends of the inside of the couplings with PVC cement and sliding the lengths of pipe together. At each end of the entire length of PVC you will need to attach one last straight coupling. At this point in time, just put the joint cement on one end of the coupling and slide that end onto the end of the last pipe in the long chain. Now you should have a straight run of PVC pipe that covers 90 per cent of the trench. The entire length will have one piece of cable running through the pipe with enough wire left over to continue the line into the building and up to the electrical box.

  6. 6

    Measure from the edge of the PVC pipe to the end of the trench. Subtract 10 cm (4 inches) from the measurement and cut a length of PVC pipe to that length. Do this for both ends of the pipe.

  7. 7

    Coat both ends of the PVC pipe (the one you just cut in Step 6) with the cement. Then slide one end of the straight piece of plastic pipe into a 90-degree elbow. Now slide the two connected pieces over the wire with the long end going first. Slide the whole unit along the course of the wire until it reaches the coupling at the end of the pipe that is sitting at the bottom of the trench. Join this piece to the PVC pipe in the trench. Do this on both ends of the trench. Now the length of the trench has a complete length of pipe with a 90-degree elbow at each end and a long piece of wire coming out of each elbow.

  8. 8

    Measure the distance from the elbow to the surface of the ground and cut a piece of straight PVC pipe to this length.

  9. 9

    Coat the outside of one end with the PVC cement and slide that piece into the top of the elbow. Make sure the wire runs through the centre of the pipe.

  10. 10

    Take a PVC cap (do this at both ends) that fits at the end of a 3.7 cm (1 1/2 inch) pipe and drill a 1.8 cm (3/4 inch) hole in the centre of the cap with an electric drill. Without adding any PVC cement, slide the end of the wire through the hole in the cap and push the cap until it comes to the top of the pipe at the surface of the ground. Push the cap so it fits over the end of the pipe. Don't glue it so the electrician can add a wire coupling. Now you can fill the trench with earth.

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