Choosing The Right Leak Detector from Subsurface Instruments

Subsurface Instruments has long been an industry leader in acoustic water leak detectors. With an innovative line of products encompassing an array of models and additional features, water utility professionals will be sure to find the acoustic leak detector that meets their leak detection, management, and maintenance needs.

**For a quick feature and price guide for Subsurface Leak Detectors, please refer to the following table**

An Introduction to Subsurface Instruments’ Leak Detectors

The leak detectors from Subsurface Instruments are all acoustic listening devices. These detectors are designed to identify leaking pipelines below the ground surface and to pinpoint individual leaks.

The identification of which pipelines in a system are leaking is accomplished during a water leak survey. After the survey has been completed, individual leaks can be pinpointed.

Water Leak Surveys with Subsurface Instruments:

Water leak surveys are performed by utility professionals to determine which lines on their system are leaking. These are generally conducted on a street-by-street, or line-by-line basis. During these surveys, the ground microphone is put into direct contact with hydrants, valves, or pipelines.

Since solids such as metal or plastic conduct sound better than soils this direct connection is an effective way to listen for leaks along long stretches of pipeline. The connection is generally made with a contact rod threaded directly to the microphone, or with a powerful magnet that allows the microphone to attach to an iron or steel valve or hydrant.

Water Leak Pinpointing with Subsurface Instruments:

Once a line has been identified with a suspected leak, it is time to find the exact leak location. The operator uses the microphone and walks the length of the leaking pipeline, placing the microphone on the ground every few feet. As the microphone gets closer to the leak location, the leak noises become louder. After passing the leak location, the sound will begin to decrease.

How do Subsurface Instruments’ Acoustic Leak Detectors Work

The line of leak detectors from Subsurface instruments all function as acoustic listening devices. Think of an acoustic leak detector as a “stethoscope” for diagnosing subsurface leaks in buried water lines.

What Do Leaks sound like in a Subsurface Instruments’ Leak Detector?

Leaking underground pipelines can generate a variety of subtle noises. The ground microphone on an acoustic leak detector is sensitive enough to read these noises, however it is up to the operator to be able to distinguish the sounds of a leak from the ambient environmental noises.

Leak Sounds that can be Heard with Subsurface Leak Detectors

• Hissing: Sometimes described as “whooshing” or as “radio static”, this sound will always be present in leaking pipes over 30 psi. This is the definitive leaking pipe sound. If an operator hears this sound, it is likely that they are listening to a line break.
• Gurgling or Bubbling: This sound has sometimes been described as similar to the sound of flowing streams or creeks. This noise can occur if a leak has had enough time to carve a channel for the expelled water to flow through under the ground surface.
• Thumping: Water leaving the pipe in short bursts can beat against the soil or a cavity created by the rushing water. If this occurs, the operator may hear a “thumping” sound.
• Clinking: Leaks can cause pipelines to vibrate in the ground. If a pipeline vibrates against rocks, pebbles, roots, or other utility lines, it can cause a clinking sound in the headphones of the leak detector.

Any of the sounds above can be present on a leaking underground water pipe. However, the “hissing” noise is the only sound that is present on all leaking lines with pressures over 30psi.  All other sounds, if present, can provide further indication that an operator is listening to a leak.

What Components are In a Leak Detector by Subsurface Instruments

A variety of special features are available on the acoustic leak detection devices produced by Subsurface Instruments. These features are designed to increase detection accuracy, ease-of-use, and signal reliability. However, each model must incorporate three primary components: a microphone, an amplifier, and headphones.

The Microphone: The ground microphone on a leak detector converts sound vibrations to an electrical signal via a piezoelectric crystal. Sound vibrations begin by compressing and stretching the crystal in the microphone which creates small amounts of electricity. This electricity is then transmitted to the amplifier.

The Amplifier: The amplifier receives the electrical signals created by the crystal in the microphone and runs them through a series of current amplifiers. Using feedback loops, these signals can be multiplied hundreds of times and bring the sound into the range of human hearing. The signals are then passed into the headphones via a connecting cable.

The Headphones: The headphones translate the electrical signals received from the amplifier into sounds that can be heard by the operator. Headphones are also useful for blocking out environmental noises which can otherwise overwhelm the sound of leaks or are distracting for operators.

While all Subsurface Instruments acoustic leak detection devices have the basic components listed above, there are various additional features available which can increase the utility of the device. These range from digital and analog meters to computers that can store readings for future reference. These additional features will be covered later in this article.

Features Available on Leak Detectors by Subsurface Instruments

All acoustic leak detectors include a ground microphone, amplifier, and headphones. However, Subsurface Instruments has added an array of additional features to increase the accuracy of the devices and the efficiency with which operators can identify water leak locations.

Cut-Off Switches: The microphones and amplifiers on acoustic leak detectors are sensitive and very powerful. This allows operators to hear small or subtle leak sounds, but this also allows the system to easily become too loud for an operator. This is especially true if the microphone is dropped or if a loud background noise such as traffic is encountered unexpectedly. Sound cut-off switches allow operators to quickly cut the connection to the amplifier and reduce the noise that enters their headphones.

Contact Rods: During leak surveys, contact rods may be used with some models. By threading a metal rod into the base of the ground microphone, a direct connection to a valve, hydrant, or pipeline can be made allowing the operator to listen to the length of the line for the sounds of leaks.

Magnets: On some models, magnets are used instead of contact rods to make a direct connection with pipeline fixtures. Some models carry both magnetic and contact rod attachments.

Frequency Filters: Many acoustic leak detector models by Subsurface Instruments are equipped with noise frequency filters. These filters allow operators to “cancel out” distracting or loud background noises such as traffic, footsteps, or powerline transformers.

Digital / Analog Meters: Operators of acoustic leak detection devices rely on being able to differentiate between louder and softer leak sounds as they work along a pipeline. Small changes in sound volume can be difficult to detect by ear alone. Several models of Subsurface leak detectors carry digital or analog meters that allow a numeric value to be assigned to the sound of a leak. This allows the operator to pinpoint leak locations more precisely.

Signal Recording: Subsurface Instruments has several leak detector models that can record, graph, and store acoustic signals. This allows operators to simply walk along the length of a pipeline, placing the ground microphone every few feet. The signal recordings can then be reviewed or shared with other site personnel to identify leak locations.

Choosing the Right Leak Detector from Subsurface Instruments

An acoustic leak detection device from Subsurface Instruments is an investment that can save your organization time, money, and the frustration that arises from digging in the wrong locations. It is therefore important to select the right device for the job. The following table can help identify which product has the features that your projects require.

Our most popular model for small or single projects is the LD-7. The LD-7 is designed specifically for leak pinpointing and is compact and simple to operate. The LD-7 is also our lowest priced option and is an excellent choice for small operators or slab leak detection projects.

Our most popular leak detector from Subsurface Instruments is the LD-12. With the ability to perform leak surveys and leak pinpointing, the LD-12 also comes equipped with noise filter capabilities, a contact rod, a contact magnet, a noise cut-off switch, and a tough-as-nails carry case to help it survive in the toughest jobsite conditions. This leak detector is a popular choice for municipal water systems as an all-around acoustic leak detection unit.

Contact us with Questions about Subsurface Instruments Leak Detectors

At Precision Outdoor Tech, we want to make sure that you find the leak detector that meets the needs of your project. If we don’t’ know the answer, we will find it for you. Give us a call with your question, 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 directly below and we will respond shortly.

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