As a trainer in the locating business, I’m often approached by would-be clients who say that their techs already know how to locate, but would like a class that focuses on the tips and tricks of advanced locating. I always take these inquiries with a grain of salt and prescribe the same solution – focusing on the fundamentals of locating theory. If a tech understands locating theory, not only will most locates not require any “advanced skills,” but they’ll also be well equipped to improvise their own “tips and tricks” on challenging locates, and to recognize the difference between challenging and impossible locates (a highly underrated locating skill).
One thing that even skilled techs find daunting is locating utility systems with which they are unfamiliar or that have given them trouble in the past. For me, for years, that meant water. I came up as a contract locator responsible primarily for cable TV and electric, and the very different nature of water locating always put me off. When I started at UtiliQuest in 2004, I
had the opportunity to work with Todd Grinham, a talented veteran tech who had won the water division of the International Locate Rodeo several times. That alone leant Todd an air of detached mystery for me. Here was a guy who had managed to crack the water system – a true and living guru.
As I continued to study locating theory and refine my own skills in the field, I eventually cracked the code to water locating as well, transforming it from something I dreaded to something I enjoyed. It’s one of the very few areas of locating where I think there is an actual “trick” that is often overlooked. Of course, just like all the other “tips and tricks” in locating,
it’s nothing more than basic locating theory put into practice in the field.
Part of the problem with locating water is the fact that pipes are fundamentally different than cables. For the most part, techs work with locating relatively small, high-quality conductors surrounded by a robust insulating layer and grounded at regular intervals. This means a low-voltage alternating current (like the one produced by a locating transmitter) will travel easily down the conductor with minimal bleed off into the surrounding earth, while the far end ground acts like an attracting force pulling the signal down the line. This usually makes for easy locating at low frequencies and low power settings.
Enter the water system. With the exception of plastic systems accompanied by tracer wires, the water system flops cable locating on its ear. Instead of a relatively small, high-quality conductor surrounded by a robust insulator, a tech is faced with a large pipe not selected for its conductive abilities and surrounded by comparatively no insulator. The water system is effectively continuously grounded throughout its run. Low-voltage alternating current placed on such a system very easily dissipates into the surrounding earth with little to motivate it to travel over distance and a lot of attraction to the bounty of sweet delicious earth in contact with all that metallic pipe.
Technicians who face problems in cable locating are often used to dealing with resistance issues like poor grounds or poor soil conditions, and the solution to resistance issues often involves increasing signal frequency. Increasing signal frequency increases capacitance (or “jumping power”), allowing a locating signal to leap these locating hurdles. The higher capacitance found at higher frequencies helps solve resistance issues, but comes at the price of shorter tracing distances and higher bleedover. This is because the signal is literally leaping free of the target line.
When frustrated techs who are used to cable locating attempt to use higher frequencies on the water system, they’re actually doubling down on the inherent problem of the water system, its large surface area and nearly uninsulated contact with surrounding earth. Locating water systems at high frequencies will reduce tracing distances to a point that is often worthless.
The trick with water locating is to select frequencies that are more reluctant to leave the target conductor. That means low frequencies. Even low frequency signals are going to be reluctant to travel for long distances on the water system due to its relatively poor conductivity, so it’s helpful to give them a kick in the pants by increasing the transmitter’s output power.
I prefer a 10-watt transmitter just for this situation and have found low-frequency, high-power locating to be the key to successful water locating.
There are a couple of other things to consider with water, but the low-frequency, high-power thing has served me well and taken a lot of the anxiety out of my water locating. I still regard Todd as kind of a magician, but I think I’ve figured out one of his best tricks.
Christopher Koch is a training consultant and President of ZoneOne Locating. He is past president of Nulca and worked on both the 2009 and 2015 revisions to the Nulca Professional Competency Standard. He can be reached by email at Christopherkoch@live.com or on Twitter @kochauthor.
The opinions expressed in this article are those of the author. Damage Prevent ion Professional welcomes and encourages articles and correspondence from all points of view .