How do I find underground wires (110V, water sprinkler valves,...)? I'm
moving into a house with many underground wires which I would like to
locate. Some are live a.c. others low voltage or signaling. Is there
something I can buy/rent to do this?
In most areas you there is a "call before you dig" 800 number that you
are required to call a couple days before you do any digging deeper than
12"-16". This central dispatch service notifies the various utilities in
the area (power, phone, cable, etc.) who will come out to locate and
mark their cables. This service is free and will take care of those
If you're nice and they aren't in a hurry you might be able to talk one
of the utility folks into locating other feeds for you. If not it's
possible that one of the big equipment rental companies like United
Rentals or Nations Rent may rent the locator equipment.
The locator is really easy to use, there is a signal injector that you
just clamp around the wire (outside the insulation, no stripping or
contact with the wire) that injects a locator signal onto the line. You
then take a detector that looks a bit like a metal detector and wave it
across the ground locating the strongest signal and marking with the
little flags or paint. You just work out from the known starting point
marking as you go.
When you have everything located, take pictures and measurements and
file them away safely for future reference. If you dig in the future
you're still required to call the utility locator folks, but having the
map of the locations already helps a lot when planning projects.
This is for public utilities, not privately owned ones, which is what the OP
Sprinklers, low voltage freeds, and wiring to outbuildings, outlets, or post
lamps would all be private wiring and is not in the public record-- at least
where I'm from.
I noted that. Locate all the utility lines first. If one of the utility
guys is nice and not in a hurry you may be able to get him to locate the
others. If not you need to find a rental locator unit. Watching the
utility guy use his locator will teach you how to use the rental one.
I did have to find some sprinkler valves recently. I would dig near a
sprinkler head (those aren't so hard to find if the system works) and
look for wires running along the pipes. In this system, I would find
some number of red wires (one for each valve I hadn't gotten to yet)
and one white wire (common, present if any red wires are too).
Call your local underground utility locating service.
In addition to making the arrangements to have your PUBLIC lines located, they
may be able to suggest a contractor that will locate PRIVATE lines.
In the past, I have, as a courtesy, located ONE private line (or two) for a
good customer. These days, locators are so very pressed for time that such
freebies are probably nonexistent.
Plastic water lines (no metal) CANNOT be located by COMMON locators.
Nonmetallic lines (gas, etc) are usually placed along with a 14-12-gauge
locating WIRE in the same trench. Lawn sprinkler companies usually don't
bother to place such wires. Good luck!
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