How to find underground cables?

If you are trying to work on a cable or need to avoid one while digging, it is important to be able to locate it. Traditionally, the only way to find an underground cable or other utility was to check the plans and try to find it by digging. This time consuming and likely to cause mistakes. Using an underground utility locator is a much better option.

Blog how to find underground cables

The Power of a Utility Locator

As mentioned above, there was a point when the only way to find pipes and cables underground was to dig for them. Plans from when the utilities were put in place could help. However, this was almost like searching blindly. Using a utility locator (also called a pipe & cable locator), you can pick up an electromagnetic signal from the utility from the surface without any digging. This can help you to trace and mark the full extent of the pipe or cable. In other words, there is no more blind digging.

Passive vs. Active Signals

There are two ways to pick up electromagnetic signals from cables: passively or actively. In the former case, the locator uses the electromagnetic signal naturally produced by the utility. Powered lines can often easy to detect using this method. Active signals are applied to the cable by a transmitter. This is used when there are multiple utilities that would be hard to differentiate, when the cable doesn’t produce a strong enough signal by itself and for pipes that have no natural signal. Often, a comprehensive location process will involve both passive and active signal location.

finding underground cables infographic

Steps for Finding and Marking Underground Cables

Finding an underground cable is a relatively simple process if you have the right tools. However, it can require a little time and effort to locate both the target cable and any other nearby utilities.

1) Select the Right Locator

Before you try to locate anything, it is important to select the right locator. There are two major types: utility and magnetic locators. The former detects electromagnetic signals and the latter detects magnetic fields. Only iron and steel items produce magnetic fields. So, for most cables, you will need a pipe & cable locator.

2) Determine Whether You Need an Active Signal

Next, determine your location strategy. If you are looking for powered cables, you may want to start with a passive signal. As you home in on your target, you may need an active signal.

3) Apply an Active Signal If Needed

If necessary, connect your transmitter to the cable you are trying to find. This will send a distinct electromagnetic signal through the cable. Your receiver can differentiate this active signal from other, passive signals.

4) Identify the Likely Location of the Cable

Before you start to sweep, it is helpful to make an educated guess about its location. This can often be achieved with surveyor’s plans or the plans from when the utility was put in place.

5) Sweep With the Locator

Starting with lower sensitivity, move your pipe & cable locator in broad sweeps over the ground. Moving slowly and methodically, try to locate the target signal.

6) Narrow Your Search

As you begin to find the signal with a coarse sweep, increase your sensitivity and make small sweeps. Gradually, you will find a place where the signal is at its strongest.

7) Mark the First Cable Location

Using some sort of marker, indicate where the first positive signal is coming from. Common tools include stakes, surveyors’ nails and paint. If you intend to come back at a later date, a surveyor’s nail may be the best choice. This can be found again easily by detecting its magnetic field.

8) Trace the Cable and Mark Each Location

Moving gradually, follow the signal of the cable. Mark its path from the surface for the relevant area. Make sure to check for other utilities in the same area before you begin to dig. It is a good idea to check both for passive electromagnetic signals and magnetic fields.

Order Your Underground Utility Locator Today

With the right tools, you can find and locate cables, pipes and ferrous objects underground. Engineer Supply has a broad selection of surveying and construction tools to help you will all your utility work. Check out our selection of underground utility locators to get started. We are happy to help you find the right tool for your unique needs.

Frequently Asked Questions

How Can I Order a Utility Locator?

Blog how to find underground cables

You can order magnetic and pipe & cable locators from Engineer Supply. We have a broad range of tools for every job. In addition to the locators themselves, we also have accessories and related tools such as surveyor’s nails. In short, you can order everything you need for the job from Engineer Supply.

What Is the Difference Between a Pipe & Cable Locator and a Magnetic Locator?

The difference between these two types of locators is what they detect. A pipe & cable locator can find either passive or active electromagnetic signals. Conversely, magnetic locators find magnetic fields and their poles. This is valuable for finding iron and steel objects underground.

Do I Need Both Locator Types?

This depends on the type of work you will be doing. It is almost always important to check for underground utilities before beginning any excavation. If you are confident that there are no steel or iron objects underground, you may not need to use the magnetic location tool.

How Should I Mark Cable Locations?

You can mark cable locations with any system that works for you. Some people use simple stakes or paint depending on the surface that they are checking underneath. In some cases, it is helpful to use surveyor’s nails because these can easily be found again using magnetic location.

What Types of Work Require a Locator?

Any work that involves digging should be preceded by using a pipe & cable locator. Simply put, digging without identifying the locations of utilities is an almost sure way to cause an accident. It is also illegal in many cases. Similarly, it is important to use a locator to find utilities when they need repairs or other work.