Drain Pipe Locating Tracing Marking


Knowing where to dig


When working on drainage systems, it’s important to save time by eliminating random digging. Knowing where to dig has always been a problem, whether is was digging to find water for a well, or to find buried treasure. Dowsing, the pseudoscience of finding underground objects by divination, has a long history. Dowsers use such tools as pendulums, dowsing rods, or forked sticks to search. Little evidence exists to show that dowsing is in fact effective, however.

But good technology exists for plumbing and drainage applications. As metal detectors grew in popularity for people searching for underground metal, the realization came that the same technology could also detect ferrous metals in piping systems.

Modern metal detector

Today, inexpensive radio technology now makes it possible to find such things as lost keys. This technology can detect the location of even non-metallic underground piping, such as PVC.

Key finders
Key finders

Detection systems

Detection systems today use the same technologies of metal detecting and radio signals to find drainage pipes and other underground objects. Systems typically consist of a locator, held by the person searching for the drain pipe, and may also include a device to create a radio signal by either introducing an electrical current into the piping system, or by inserting a radio transmitter into the system.


Locators generally are handheld and battery-powered devices that give audible and/or visual indications of how close they are to the source of the signal they detect. They can guide the operator to the location nearest to the transmitter, and indicate the depth of the target.


Locators can have graphical indicators that show signal strength, direction of the pipe, direction to move to follow the pipe, whether other objects are interfering with the trace.

Magnetic locators (passive technology)

Magnetic locators find ferrous metal objects, such as valves, manhole covers, iron piping and iron pipe joints, gratings, and so forth. These locators can discover objects as far as 15 feet (5 meters) beneath the ground.

Radio detection locators (active technology)

Many components of drainage systems are non-ferrous, and in those cases an active detecting technology is used. Pipes and cables can be detected by either having them carry an electrical signal that can be detected above ground, or by sending a radio transmitter into the piping.

Line Transmitter

A signal inducer runs an electrical current through the piping (or wiring) and that current created a radio signal can be detected on the surface by the locator device. The current is put onto the pipe through either electrical clamps or using an inducer if the metal of the pipe is not accessible (as for example when it is covered with insulation).

Wired sonde

A signal can also be created by inserting a signal generating device (a “sonde”) into the pipe, either on the end of a cable or as a free-floating device.

One individual has even used an inexpensive key locating device as a rudimentary sonde, but it is very limited in its capabilities, reaching only through a few centimeters of earth.

Pipe locators match well with remote inspection cameras, making it possible to both see what the problem is, and where it can be found.

If you are interested in locating underground drains on your property, Master Drain can assist.

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