Without the right information and tools, locating and mapping underground pipes is challenging. Incorrect property diagrams, outdated utility maps and unreliable tools can all strike together. It’s frustrating, and especially so when you need to find the pipes without breaking soil. Given the complexity of the infrastructure buried beneath our feet, it’s a wonder anyone finds anything at all.

When it comes to finding underground pipes, however, there are other tools better suited to the task. Ground-penetrating radar, or GPR, is the tool that many use to ease their pipe-finding frustration. It’s a proven method to reliably locate, measure and map underground objects. Whether it’s copper pipes or PVC — where traditional methods falter and fail, GPR excels.

Why Use GPR to Find Underground Pipes

a deep sinkhole on asphalt with cracks

If you’re considering GPR as a solution to locate underground pipes, you already understand the inherent value of this method. We all know the words: Call before you dig. This mantra seems like common sense. However, every year, there are reports of millions of dollars in damages and countless injuries as a result of not knowing what’s below.

Nowadays, underground infrastructures are growing increasingly dense and complicated. And despite the best-laid plans of all involved, diagrams, maps and schematics don’t always reflect what’s in the ground. Given these challenges, GPR’s nondestructive yet highly effective approach is invaluable. Operators leveraging it for locating underground pipes have a razor-sharp advantage over those who don’t.

GPR doesn’t only locate pipes. The inherent technology makes it effective at locating nearly any type of buried object. And with only a couple of exceptions, it works in nearly any subsurface material, from soil and rock to concrete and asphalt. A high-quality GPR system helps you:

  • Locate steel reinforcements in concrete at a construction site
  • Scan pavement and asphalt to identify compromises in the structure
  • Identify sinkholes, voids and other underground disturbances

Most importantly, GPR provides accurate information as to what’s buried beneath the soil. And while this data is viewable in real time, it’s also sharable with others involved in the project. Reliable data eases the decision-making process for all involved, whether you’re digging a hole or planning a major construction project.

With the right system and scanning strategies, GPR even provides accurate 3D data of the subsurface material, delivering unprecedented clarity without ever sinking a shovel. Whether you’re in the business of locating utilities or need a reliable solution for mapping subsurface infrastructure for construction, GPR is an invaluable tool.

How GPR Works to Locate Underground Pipes

underground plastic pipe

Ground-penetrating radar works by way of electromagnetic radio waves transmitted from an antenna attached to a rolling cart. If you know how sonar works, it’s the same idea. When a wave hits an object, it bounces back up to the antenna. The system collects data from this reflection to provide visual feedback to the operator.

The feedback tells the operator how deep the object is by measuring the distance the wave traveled from point to point. And because the waves reflect off different objects in different ways, operators can understand what the object is by analyzing the images. Underground pipes, for example, are often visualized as hyperbolic arches — the sharper and higher the arch, the smaller the pipe.

All of this is what makes GPR especially effective at locating underground pipes. Many of these pipes are often made from PVC or other non-metallic materials. In these situations, other subsurface surveying methods are unreliable at best or completely ineffective at worst. With GPR, metal and plastic both reflect electromagnetic waves.

Scanning for Underground Pipes

underground pipes buried in sand

With a high-quality system, such as our Quantum Imager, locating underground pipes isn’t just effective — it’s also relatively simple. Knowing the general location of the pipes and which direction they’re running helps speed up the process. Before getting started, be sure to check any schematics or blueprints for clues, if they’re available.

Once you know where you’re scanning, the process looks like this:

  1. Roll the unit in a straight line, perpendicular to the direction the pipes are running.
  2. When a reading appears, back the unit up and mark the location with a flag or paint.
  3. Move the system a few yards down, following the direction the pipes are running, and repeat the process.

In situations without the information needed to narrow down the target area, GPR still works impeccably — you’ll just need to walk a bit more. If this is the case, the same approach applies, but you’ll want to plan your survey and take a grid-based approach. By moving your scanning lines further apart and marking the areas you clear, you eliminate large swaths of the target until you eventually zero in on the pipes you’re searching for.

One final consideration: At survey sites with significant underground infrastructure, it’s not always easy to differentiate one pipe or line from another. Various utility lines often run parallel to each other. Schematics help in this situation, but in others, you may need to do a little more leg work and trace the lines back to some other known infrastructure, such as a valve or meter.

What Kind of Underground Pipes Can GPR Find?

an underground gas polyethylene pipe

Because you can locate virtually any underground object with GPR, underground pipes are no exception. While GPR does have its limitations, covered below, in most instances, GPR can detect any kind of pipe imaginable — even older clay pipes. Here’s a list of just some of the pipes and related structures GPR can locate:

  • All manner of metallic pipes, including copper
  • Any kind of non-metallic pipe, including PVC
  • Sewer systems and underground storm drains and runoffs
  • Underground plumbing, septic tanks and related infrastructure
  • Utility lines or pipes where tracer wiring has failed

Underground water pipes and mains are one of the biggest reasons operators turn to GPR. Because this kind of infrastructure is often made from non-conductive materials, they’re beyond what traditional surveying methods can handle. And while tracer wires and acoustic tracing are nice approaches to have handy, they aren’t always practical. Because GPR has no qualms with these objects, it’s perfect for locating and mapping any kind of underground pipes — water or otherwise.

The Limitations of GPR

detecting underground pipes in wet, swampy soil is one of the limitations of GPR

For many operators, GPR is an invaluable tool — one they turn to again and again for countless scenarios. But anyone in the business of finding underground objects knows that most situations often require more than one approach. While GPR is incredibly effective, the technology isn’t without limitations.

To understand these limitations, it helps to look briefly at the science behind GPR, which lies in electromagnetism. All materials have what’s called a dielectric constant. This value indicates a material’s conductivity — the higher the value, the more conductive it is. When the electromagnetic waves used by GPR encounter high-dielectric materials, they’re essentially scattered and absorbed.

As you can probably imagine, water has a high dielectric constant; it’s very conductive. And so, in conditions with high water content, such as a flooded field or environments with wet clay, GPR doesn’t fare as well. Put simply, wet, swampy soil is GPR’s Achilles’ heel.

That said, a little rain or snow won’t cripple a high-quality GPR system. In fact, this limitation even becomes a feature in some situations, such as locating underground water or identifying burst water main. As long as you aren’t surveying marshland, GPR will serve you well.

Transform Subsurface Surveying With US Radar

two people dig at an archaeological site

We’ve heard it time and again from our loyal customers — our products have become central to their professional approach. Whether they’re professional operators locating utilities or field archeologists searching for artifacts, GPR is foundational for them. Some have even built businesses by leveraging our products to locate objects for other clients and businesses. If you’re looking for a way to change how you approach subsurface surveying, we have no doubt that one of our GPR solutions will do just that.

At US Radar, we’ve spent the last three decades engineering innovative commercial systems that stand on the cutting-edge of GPR capabilities. More than that, we design our products for the field — not for a perfect lab. We offer a variety of solutions to match any and every scenario, all of which are reliable, dependable and easy to use. And if you ever need assistance in the field, our worldwide network of representatives is there for support and training. If you’re ready to see how GPR can help you, get in touch with us today.