Why is Tracer Wire Important?

The most widely used form of locating underground utilities is EM or electromagnetic locating. The principles if EM locating involves the application of an Alternating Current, generated by the transmitter, and then tracing the electromagnetic field around the pipe or cable with a receiver.

The phenomenon of electromagnetism was discovered back in 1831 by Michael Faraday and is one of the Laws of Physics. For an Electro Magnetic field to be formed the Alternating Current needs to be applied to a metallic and conductive line.

Unfortunately, many utilities these days such as potable and waste waters, gas, fibre optics, are commonly made of materials that are not metallic and conductive. This means that the most used form of locating equipment is useless when trying to locate these services – well done Mr Asset Owner.

Just like any circuit that you are trying to trace, it MUST be a complete electrical circuit, by that I mean that both ends of the trace wire needs to be earthed. If not, the circuit is “open” and the signal is lost and thus becomes untraceable. The goal is for the signal to be carried all along the trace wire before it returns to the transmitter, through the soil (mother earth).

It has been identified that there are common reasons why you cannot locate a trace wire installation:

1. Dead Ends are not Grounded.

The dead end, also known as the far end, must be grounded properly. In order for signal to reach the target, it MUST have a stronger “ground” than anywhere else along the target line. If the tracer wire is not properly grounded, the signal will escape and return to the transmitter before reaching the target. It is important to remember that electrical signals are Pulled, not Pushed so for the signal to travel along to the target, the earth at the dead or far end has to be sufficient to Pull the signal down the line.

So, what happens when plastic pipes need to be located?

Hopefully, the asset owner has used some common sense and has had a Trace Wire installed with the utility. During installation, the tracer wire is buried along the length of the pipe. The wire is often taped to the outer edge of the utility at regular intervalss to keep it attached to the utility and protected from damage.

Then when the pipe needs to be located, the locate technician attaches one end of his conductive connection leads (usually the red end) to the trace wire, places the earth stake into the ground and connects the other lead to it (Black clip). The transmitter is then connected a frequency is selected (start low) and the trace begins.

2. Grounds are not Equal.

When there are “potential grounds along the path, they complete for the electrical signal, and we know from our training that electricity will always follow the path of lease resistance, in which case the strongest earth will win. Unfortunately, if the strongest ground is not your target, you will lose your signal and not be able to locate your target line.

3. Bad Connections.

Any tracer wire system is only as good as its weakest link, in other words its poorest connection. The use of correctly graded connection hardware, for example being water and corrosion proof will protect vulnerable wire joints and connectors and ensure suitable continuity for the electrical current flow. Corrosion causes resistance to the flow and in worst cases, a complete breakdown of the system.

4. Tracer Wire not designed for Underground Installation.

Tracer wire should be insulated and be designed for underground usage. HDPE, which is high density polyethylene is the most common material used. Other materials, such as THHN, which is a nylon coating, deteriorates rapidly, and leaves the conductor exposed to the soil, water and potential corrosion, as well as creating another point for improper earthing to occur.

5. Poorly Made Tracer Wire

Multi-million dollar buried infrastructure deserves to have quality tracer wire capable of carrying a detectable signal. The signal does not have a chance on broken or corroded wire.

Correctly installed Tracer Wire Systems are our best defence in protecting non-metallic underground utilities.

One final word, it may seem obvious, but I have seen mistakes made in the past. When connected to a trace wire, you are NOT locating the service, you are locating and marking the position of the Tracer Wire. As always, potholing is the key to being 100% accurate and confirming the utilities’ location.