Locating buried electrical cable/conduit in yard

Question

Our house, which we purchased about a year ago, has a shed in the back of the yard which has electricity and is roughly 100 ft away from the main house. From what I can tell the previous owner had cable run to the shed through a conduit that exits the house at the closest exterior corner. I see the same conduit exiting the house and entering the shed.

My problem is that I have no idea what path the previous owner took to run the cable out to the shed, or if the conduit is even at code rated depth, and we're looking to do some landscaping and possible run a water line out near the shed. I'm assuming 811 isn't going to locate privately run cables in the ground, so is there a tool or service I can use for this? Just based on the unknowns I would prefer to stay away from the conduit entirely.

Answer 1

Step zero - to reduce any nerves associated with digging, turn off the breaker supplying the shed at the house end.

Step one - assume a straight line from the endpoints you can see, as the most likely path in many cases. Dig a little bit, carefully, along the conduit as it enters the ground, and see if the direction it points underground matches up.

Step two - very carefully go prospecting along the straight line. Try close to one end and dig with a trowel or very gently with a shovel, looking to see if they were smart enough to put "buried electric line below" tape in the top of the trench. Not would be no surprise, having it would be a helpful and pleasant surprise. You'll also get a sense of the depth, and whether they used conduit the whole way or not. You may also see a different backfilling (soil type) the immediate area of the conduit, which you can use as a clue later.

Step three - go further out and dig again - go to the middle if step two supports the "straight line" path.

Alternate step one - hire a private contractor to trace the line, or try renting equipment to do the same yourself. It's tricky enough to use (sorting out confusing signals, etc.) that the experienced operator might be better, but DIY can work. Check with your tool rental place. Something like location service might be a heading to look for a contractor, or you might ask the irrigation folks if they know who to call.

Answer 2

You can use a metal detector, but find someone who knows how to use it. Different models can find wire down to 2-3 ft if used properly by an experienced person.

Source: I use metal detectors.

Answer 3

It is often possible to confirm the location of buried AC power cables by sending a low frequency signal down one of the lines and picking it up from the surface with an AM radio dialed to the lower range of the AM band. A strong signal can be induced by winding a narrow gauge wire (18 or 20 gauge) half a dozen times around the spark plug cable of a four-stroke engine (lawnmower or other), attached the other end of the narrow gauge wire to one end of the (disconnected from power) cable that you want to find, started the lawn mower, then sweep the portable AM radio over the ground surface near the location you know it is buried -such as where it leaves the house or enters the shed. The mower magneto induces a signal onto the buried 2.0-gauge cable which the AM radio picks up as an identifiable pulsed static. You can track the signal over the ground surface if you stay right above the cable and it is not buried to deep.