November, 2017
Inspection News and Views from the American Society of Home Inspectors

Chasing Water With Thermal Imaging, Part 1


Chasing water is what I do for a living. I’ve found thermal imaging to be an excellent tool that complements any leak detection strategy. With the understanding that water always chooses the “path of least resistance,” we can use thermal imaging to help explain the often-mysterious origins of water leaks, which may be far from the physical evidence of damage.

Thermal imaging technology has allowed me to expand my business by mapping paths with a completely noninvasive technique. Thermal imaging provides immediate visual results that can reveal the actual sources of leaks. This article details how my company has helped many clients solve their “mystery leaks.”

The Path of Least Resistance
People tend to choose the path with the least number of steps or the fewest obstacles to achieve a goal. Computer navigation systems offer the shortest distance between points A and B or provide a route with the least amount of traffic. As defined by, “the path of least resistance describes the physical or metaphorical pathway that provides the least resistance to forward motion by a given object or entity, among a set of alternative paths. The concept often is used to describe why an object or entity takes a given path.”

Water, of course, is known to follow the path of least resistance. Think of how a river, seen from above, follows a long, snake-like path. Water, unlike human beings, doesn’t care how long it takes to get to its final destination as long as it travels along the easiest route. This fact is often what confuses people when it comes to understanding where a water leak originates, as they commonly assume the leak must be near the area of visible damage. Having been in the building inspection business for more than 20 years, the number of times I’ve encountered people frustrated with “mystery leaks” is huge—it’s such a common problem that as a key word search on the Internet, it yields nearly 10 million results.

Aerial views: Left, one segment of a river’s actual course indicated by yellow lines measures 14,508 feet; right, the distance between the same starting and end points on the river measures only 5,676 feet when traveled in a straight line.

Manmade waterway, notice the straight course.

What’s in the Bag?
The primary tools in my bag are my knowledge and experience. Physical tools are no substitute for effective research, clear communication, use of proper investigative techniques and thorough documentation of problems. I can then use a thermal camera, along with moisture meters, hygrometers, measuring tapes and a digital camera, to the best advantage.

Simple Science
When objects become wet (due to movement of air), a cooling effect takes place on the object’s surface—a process known as evaporation. The infrared (IR) camera doesn’t “see” water, but rather the effects of water on temperature and environment. 

The Cases
There are all kinds of leaks out there—from plumbing systems to building fenestration leaks to a surprising problem we’ll call the “take a leak” syndrome—all of which can be diagnosed with thermal imaging.

The Seven-Year Mystery
My company was retained to source the moisture of an ongoing leak taking place in a downstairs office of a two-story home. The owner asked us to perform water testing of an exterior window, as recent repairs had been done to the plumbing system and the owner did not believe that the water came from this location.

Thermal Imaging quickly identified the location of moisture; it was up to us to chase the source.

We viewed the room above, noting a colder area at the right side of toilet that, when viewed with a moisture meter, had 100% moisture. Thermal imaging was resourceful in identifying that there was a failed wax seal and a loose toilet.

Slab Leaks
We are often asked to identify slab leaks. Initially, we recommend the clients consult with a leak detection company that uses ultrasound (a licensed plumber), as they usually get good results and their fees may be less than what we charge. Based on the client’s situation, however, we do accept some of these jobs and have had great success.

This first case was reviewed by a company that used ultrasound. They did not source the leak, however, so our infrared technology quickly brought to light the problem area.

As you can see in the images, “X” marks the spot.

Another case was more exciting, in that we were able to obtain the remediation pictures that helped prove how effective IR technology (properly used) can be. In this case, the client found our company by searching the Internet for a solution to his known slab leak. Problem was, he didn’t know that the source, as the evidence shows, was 6 feet away.

These photos show a definite leak at the garage floor. The opposite area in the lower hallway showed no sign of leakage or damage anywhere.

Thermally speaking, these pictures are worth a thousand words.

By using thermal technology, we mapped out the suspected leak location. Note that the plumber is digging right at the “X.”

What do you know? “X” did mark the spot. The homeowner called me the next day to express how “upset” he was that my calculations were a whole 1 inch off! The picture on the right shows the newly repaired pipe and everything back in order.

Deck Leak
The following example shows how water travels and how, in some cases, what’s thought to be the leak actually is confirmed to be something else. A contractor suspected an upstairs bathroom leak that ended up being a deck flashing leak, so he hired us to do thermal imaging.

We mapped the moisture and showed how having a stain in one area doesn’t mean that the cause is opposite the evidence and how moisture takes the path of least resistance.

These thermal images show a time lapse of 30 minutes of water testing.

The water testing helped identify this leak to the source and in a semi-non-destructive manner. The stain in the image to the right was the final resting place of the water, as seen in the last IR image. Obviously, this was not opposite the source, which was several feet away. With technology and a little brain power, we mapped it to the root cause.

Poor Roof Design
(third time’s a charm, right?)
A persistent and never properly repaired roof led us to another case. A southern California homeowner was frustrated after her roof had been repaired three times for the same problem, but it still was not fixed. The roofing contractor suggested replacing an upper roof to solve the problem; however, the client was not convinced and instead contracted our services. 

We saw normal evidence of a bucket to capture the water. Thermal imaging immediately showed the wet area at the ceiling. The arrow at the image indicates how the water traveled, directly over the bucket. As water traveled down, ceiling to wall, exiting at the wall opening to the living room.

The wet area identified in the thermal image first was confirmed with a moisture meter to have 100% and then to the source. We viewed that the roof had a steep slope, with an upper roof cascading over it. This design was causing water to first hit the structure and bypass the counter flashing, leading to moisture entry. The suggested repair on this home involved a new design for a valley flashing versus a suggested roof replacement.

Want to see more water mysteries solved? Watch the Reporter for Part 2 of this series, which will focus on IR testing in more homes and large buildings. I’ll also share advice on marketing the thermal imaging aspect of your business.