Use Infrared to Detect Underground Leaks

Suspect a buried leak? Thermography can help you find it.

By James Seffrin, Director, Infraspection Institute

Leaks are a common problem with underground piping systems. Under the correct conditions, infrared thermography can help you detect evidence of leaks from buried systems that carry hot or cold product.

This set of images shows a thermal pattern created by a hot-water line buried beneath a street along a concrete curb. The large, amorphous shape at the center was caused by an underground leak at an expansion loop. Photo: Infraspection Institute

When a leak develops in a buried piping system, be it underground or within a concrete slab, fluid is lost to the surroundings. If a leak from a piping system that carries heated or cooled fluid is sufficiently large, a temperature change may occur at the surface of the ground or concrete in the vicinity of the leak.

Leaks from buried piping are generally characterized by amorphously shaped thermal anomalies that appear along the system pathway. The ability to detect a pipe leak will be influenced by interdependent factors including, but not limited to:

• pipe operating temperature
• pipe-system construction
• burial depth
• amount of loss
• soil type and moisture content
• ground cover.

Excavation of the exception area indicated by the hot-water line thermographic imagery confirmed that a leak in the continuous-jacket piping system had occurred in one leg of an expansion loop. In this case, infrared inspection allowed the repair team to zero in on the problem and keep excavation to a minimum. Photo: Infraspection Institute

Infrared inspections of buried piping systems located outdoors are best performed late at night with calm wind conditions. Such inspections may be performed on foot, from a motor vehicle, or from an aircraft. Late-night inspections eliminate the effects of solar loading and solar reflection. Note, however, that infrared inspections of indoor piping systems may be performed at any time of the day.

During an inspection, the thermal imager is maneuvered over the pipeline pathway. Well-defined straight lines that correspond to the location of the buried lines generally indicate a healthy piping system. Amorphously shaped thermal anomalies that can’t be explained in terms of piping-system construction or features may indicate leaks and should be marked and subsequently investigated for cause. MT

Jim Seffrin, a practicing thermographer with 30+ years of experience in the field, was appointed to the position of Director of Infraspection Institute in 2000. This article is based on one of his “Tip of the Week” posts on IRINFO.org. For more information on detecting underground-piping leaks and countless other infrared applications, as well as various upcoming training and certification opportunities, email jim@infraspection.com or visit infraspection.com.