How To Locate Underground Sewer Lines

Sewers are an important, but often overlooked part of modern infrastructure. Without underground sewer systems, the ability to live in large and sanitary urban environments would be impossible. As one of the foundational services of modern cities, our sewer systems are critical pieces of infrastructure that must be continuously maintained and improved upon. This means that the ability to locate sewer lines will remain an important skill in the wastewater treatment profession.

Reasons to Locate an Underground Sewer Line

Like any complex and critical utility system, sewer lines require routine maintenance and repairs. To service these lines, they must first be found. The proper location of sewer lines allows wastewater professionals to diagnose clogs, breaks, leaks, and other damage. Once damage to the sewer lines have been diagnosed, repair or replacement work can then be conducted as necessary.

Types of Underground Sewer Lines and Systems

Sewerage systems can generally be divided into two categories: private and public. Private sewer lines usually run directly to a septic tank or drainage field. Septic tanks require pumping services from time to time, but beyond that, private sewer systems require fairly minimal maintenance.

Public sewer systems are generally operated by towns, cities, or other municipalities. Small sewer lines drain from business locations and individual residences to sewer mains that are usually located under alleyways and streets. The sewer mains generally flow into a wastewater treatment plant which sanitizes the sewage before releasing the cleaned water back into the environment.

Difficulties in Finding Underground Sewer Lines

When a new sewer line is connected to a municipal system today, the location is usually entered into mapping software using highly accurate GIS systems. For sewers 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 city plans with a pen or pencil.

For many municipalities, these maps can be notoriously unreliable and many smaller sewer service organizations have traditionally relied on the knowledge of senior employees to identify older sewer line locations. The downside to this is that, as the older generation of wastewater professionals retire, the knowledge they have of system locations can be lost, leaving new wastewater employees wondering where the pipelines in a system might be located.

Underground Sewer Line Locating Equipment and Methods

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

Traced vs Non-Traced Underground Sewer Lines

For the purposes of locating underground sewer lines, pipeline materials can be divided into two broad categories: conductive and non-conductive. Conductive lines allow electrical signals to be transferred along the length of a sewer line. Typically, materials for these lines are either ductile iron or cast iron. Non-conductive pipeline materials may include plastic/PVC, ceramic, concrete, and asbestos.

Non-conductive lines can be more difficult to locate, and wastewater engineers 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 sewer locating device is most appropriate for the job at hand.

Sewer Cameras / Sondes

Modern advances in camera technology have allowed plumbing professionals to trace sewer pipelines while recording high quality videos. This allows sewer camera operators to not only identify damage such as breaks, clogs, or tree roots, but also to precisely locate the damage before beginning repairs.

Many sewer camera heads are now equipped with sondes. Sondes emit an electromagnetic frequency as they move through the sewer line. This frequency can be read by the receiver from a utility locator and will allow the wastewater professional to trace the camera head as it moves along the sewer line. When the camera / sonde arrives at the damage or obstruction, the operator can mark the precise position of the issue before starting excavation work.

Utility Locators

Utility locators have long been used to find conductive and traced sewer lines. These types of locators work by using a transmitter to project an electromagnetic signal along the length of a metal sewer line. If a sewer line is made of non-conductive material such as ceramic, a sonde, metal core trace rod, or sewer snake may be used to create a conductive pathway for the signal to follow. 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 sewer pipeline by using either conduction or induction.

Conduction: Involves a direct connection between the transmitter and a metal sewer line, sewer snake, trace rod, or trace wire. 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 pipeline to be traced and emits an electromagnetic signal into the ground near the pipeline. This signal induces an electromagnetic signal in the pipeline, sewer snake, trace rod, or trace wire.

Magnetic Locators

Magnetic locators can be used to find sewer lines if they are made of ferrous materials such as iron or steel. They can also be used if a non-conductive sewer line is equipped with ferrous joints or valves. A magnetic locator is limited in scope since it can only read ferrous components. However it can be the ideal tool to find buried septic tanks if they are made of steel. The large size of a septic tank allows a magnetic locator to read it 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 back 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 pipelines as well as storage or settling tanks constructed of any material. These locators are an excellent all-around tool for identifying all types of materials in areas that are relatively free of other buried materials such as rocks, concrete, and tree roots.

Choosing the Right Underground Sewer Line Locating Device

Selecting the right sewer line locator device for your projects depends on the type of sewer lines that you will be locating, the environment in which they are located, and the reason for the locating activity.

Best Sewer Line Locators for Plumbers

If you are a plumber or plumbing contractor, a sewer camera equipped with a sonde and paired with a utility locator receiver makes an excellent all-around locating package. This combination will provide the ability to trace line locations, to pinpoint blockages or damage, and to record videos for your clients when preparing quotes.

Best Sewer Line Locators for Wastewater Service Providers

If you are a municipal wastewater service employee, your projects are likely to be located primarily on sewer mains. A good locating package would include a traditional utility locator kit along with a supplementary All Materials Locator (AML) to help locate plastic or PVC lines that have not been fitted with a tracing wire.

Best Sewer Line Locators for Septic Service Providers

Septic Service providers will benefit from a kit similar to those recommended in the plumber’s section above. In addition, a septic service professional may want to add a magnetic locator which will aid in the identification of septic tank locations and steel or iron septic valves.

Contact us with Questions about Underground Sewer Line Locators

If you are deciding on whether to purchase a locator for underground sewer 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 sewer 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 sewer line project, you can find our product collections via the following links.

Sewer Cameras

Work great for tracing non-conductive pipelines with the help of a utility locator receiver. Sewer cameras can also record videos of pipeline interiors to inspect for damage. Match with a sonde for even more precise locating.

Utility Locators

Utility locators work great for tracing conductive pipelines or trace-wire equipped plastic and ceramic 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 sewer pipeline types, including non-conductive materials. All Material Locators work best in non-rocky soils away from tree roots.