How to Locate Underground Gas Lines

Natural gas, LPG, and propane pipelines deliver heating, cooking, and laundry fuels to homes and businesses around the globe. These systems are safe, efficient, cost effective, and clean. These gas distribution systems are important in maintaining the quality of life that we have come to expect in modern society.

Reasons to Locate Underground Gas Lines

There are many reasons to locate underground gas pipelines. The most common is to prevent line strikes during work on other utilities or during construction activities. Gas pipelines might also be located to complete necessary repairs or upgrades to systems.

Types of Underground Gas Lines

Gas pipelines can be made of several types of materials, each with their own strengths and weaknesses. Below is a summary of common materials used for building gas pipelines.

Black Steel Gas Pipelines

Black steel pipelines have been used in the gas utility industry for years. Although labor intensive to install, pipelines built from this material will last for years. It is easy to find fittings for black pipes and the smooth black oxidation on the exterior surface helps to prevent corrosion which extends the life of the pipeline.

Polyethylene Gas Pipelines

Polyethylene is a form of plastic which can be used for the transport of gas. If pipelines are to be built of this material, it must be rated for gas and this is usually indicated by a yellow color. Polyethylene pipelines are best suited for underground gas lines and indoor service lines. They should not be used where they may be exposed to light, as this will cause the pipeline to break down over time.

CSST Gas Pipelines

Corrugated stainless steel tubing or “CSST” is a flexible stainless steel pipeline material that is usually coated with plastic or polyethylene. If the pipeline is rated for gas, it should have a yellow color. These pipelines are typically used for interior gas piping components such as connections to gas burning appliances.

Copper Gas Pipelines

Copper lines were used for the transportation of gas in residential and commercial buildings for years, but they have almost been completely phased out. The installation of new copper piping for gas lines is not recommended and is typically not code compliant due to the potential for corrosion in copper pipes and fittings.

Difficulties in Finding Underground Gas Lines

When a new gas line is connected to a utility provider’s system today, the location is usually entered into mapping software using highly accurate GIS systems. For gas lines constructed before the 2010s, however, there is a good chance that no map was produced at all. If a map was created, it was generally hand entered onto computer mapping systems or drawn onto company plans with a pen or pencil. For many gas utility providers, these maps can be notoriously unreliable.

Underground Gas Line Locating Equipment

Fortunately, a variety of tools are available to gas utility professionals to aid in the location of underground gas lines. These locators can help eliminate time consuming and expensive guesswork on gas line repair and replacement projects. The type of locator used is dependent on several factors including the material of the gas pipeline being that is being located, the presence or absence of conductive tracer wires, and the environment in which the gas pipeline is buried.

Traced vs Non-Traced Underground Gas Pipelines

For the purposes of locating underground gas lines, pipeline materials can be divided into two broad categories: conductive and non-conductive. Conductive lines will allow electrical signals to be transferred along the length of a gas pipeline. Typically, materials for these lines are metals such as black pipe, CSST, or copper. The most common non-conductive pipeline material is polyethylene.

Non-conductive lines can be more difficult to locate, and gas utility workers often install copper trace wires along sections of non-conductive pipelines to help in future locating efforts. The presence or absence of trace wires or conductive pipeline materials will determine which gas line locating device is most appropriate for the job at hand.

Utility Locators

Utility locators have long been used to find conductive and traced pipelines and are still the “go-to” location device. These types of locators work by using a transmitter to project an electromagnetic signal along the length of a metal gas pipeline. A receiver wand is then used to scan the ground along the length of the line.

Utility locator transmitters can create a signal along a gas pipeline by using either conduction or induction.

Conduction: Involves a direct connection between the transmitter and a metal gas line. This direct connection is usually made with connector cables and a ground stake which is used to complete the circuit. Direct transmitter conduction is usually more powerful than induction and allows the pipeline to be traced at a further distance from the transmitter box.

Induction: Involves indirect signal transmission. The transmitter box is placed over the gas line to be traced and emits an electromagnetic signal into the ground near the pipeline. This signal induces an electromagnetic signal in the pipeline.

Magnetic Locators

Magnetic locators can be used to find gas lines if they are made of ferrous materials such as black pipe or CSST. They can also be used if a polyethylene line is equipped with ferrous joints or valves. A magnetic locator is limited in scope since it can only read ferrous components. However, if there are ferrous fittings or pipeline sections, a magnetic locator can potentially read the line at far greater depths than a traditional metal detector.

Subsurface Instruments produces a combination utility locator / magnetic locator known as the PL-TT. This powerful locator incorporates the advantages of both a magnetic locator and traditional utility locator systems.

AML / All Material Locators

All Material Locators or “AMLs” are produced with proprietary technology by Subsurface Instruments. An AML works by projecting an ultra-high radio frequency into the ground. When a signal is reflected to the receiver, it is interpreted by an onboard computer and the operator is alerted to any density change.

This technology allows the user to search for any item with a density different than the surrounding environment. This can include both conductive and non-conductive gas pipelines. These locators are an excellent all-around tool for identifying all types of pipeline materials in areas that are relatively free of other buried materials such as rocks, concrete, and tree roots.

Choosing the Right Underground Gas Line Locating Device

When considering purchasing a gas line locating device, the most important considerations are what type of pipeline material will you be locating and what environment do you expect it to be buried in. For most pipelines built of metals such as black pipe, a utility locator is likely going to be the best choice.

For polyethylene pipelines, the locating device will be determined by whether the line is equipped with a trace wire. If there is a trace wire, a traditional utility locator will still be the best option. If there is no trace wire, or if you suspect that the trace wire is broken, there are two options.

If it is believed that a pipeline has a broken trace wire, a ground fault locator such as the A-Frame by Subsurface Instruments can help to locate the trace wire break for repairs.

If there is no trace wire, an All Materials Locator or AML should be considered, especially if the gas pipeline is not buried in rocky soil or near roots. A magnetic locator may also be useful for a non-conductive pipeline if it has steel or iron valves or joints.

For an all-around locator kit that can cover any gas pipeline locating situation, a combination of the PL-TT Utility Locator / Magnetic Locator and the AML Plus all materials locator will cover nearly all gas pipeline materials and potential locating scenarios.

Should You Locate Underground Gas Lines Yourself?

Gas is safe, economical, and efficient. Unfortunately, due to the flammable nature of gas, line strikes and breaks can be expensive and very dangerous. It is always advisable that gas and other utility lines are located prior to breaking ground on a project.

Private utility location services are generally provided free of charge through your state’s 811 telephone line. Calling 811 automatically routes you directly to your local 811 center and each state has its own specific locating guidelines. If your state accepts online requests from homeowners and contractors, you may be able to file an “online request”.

If you are a contractor, or a gas service provider, utility location tools can also be useful devices for double checking locations provided by the 811 service. A second reading is never out of place and ensures that all lines have been located properly. Having a utility locator on hand can also be useful in time sensitive projects where an 811 technician may not be able to arrive immediately.

Contact Us with Questions about Underground Gas Line Locators

If you are deciding on whether to purchase a locator for underground gas lines, please feel free to reach out to us at Precision Outdoor Tech. We will discuss your needs and project specifications and will point you in the right direction to a line of products that can help you to locate your gas lines. Give us a call with your questions, and we will be happy to help you out. If it is after hours, please use the contact form listed in the municipal contact section below and we will respond shortly.

If you have already decided on the type of locator that you would like to use for your gas line location projects, you can find our product collections via the following links.

Utility Locators

Utility locators work great for tracing metal gas pipelines or trace-wire equipped polyethylene gas lines.

Magnetic Locators

Magnetic locators are ideal for steel, iron, or cast-iron pipelines, valves, and pipeline joints. The size of the target determines the depth at which it can be read.

All Material Locators (AMLs)

For all gas pipeline types, including non-conductive materials. All Material Locators work best in non-rocky soils away from tree roots.