Can a hidden leak be found without opening a wall?
Sometimes. A thermal camera and a meter can point to a leak from the outside of a wall, but they do not always show the exact source, and an opening may still be needed to confirm it.
The camera works best when there is a temperature difference between the water and the surrounding material. In a warm room in winter, a cold supply leak can show clearly, while in summer the difference may be too small to see. The result depends on the conditions in the room that day.
When the camera and the meter do not agree, the crew makes a small opening to check. An opening that is small and carefully placed is the cheapest way to confirm the source.
What if the leak is under the slab?
A slab leak is harder to reach. The plumber and the water-damage crew work together to find the line, and the choice of where to open the floor is made with the homeowner.
A line under a slab is covered by concrete, and the repair often means cutting an opening in the floor. The thermal image and the meter show the area most likely to hold the leak, but the exact point is confirmed with a pressure test or by opening the slab at the narrowest point.
The homeowner is shown the proposed opening before it is made, and the plumber gives the expected repair. The cut is made only where the readings and the test agree.
Does the detection work cost less than the damage?
Usually, when the leak is found early. A hidden leak that runs for months can soak framing, flooring and the insulation, and the cost of the drying and rebuilding is far greater than the cost of finding the leak.
Finding a leak early limits the area that must be dried and the number of materials that must be replaced. The longer a leak runs, the more the wall and floor are damaged, and the repair grows with it. The homeowner can decide how far to go based on the findings.
The detection work does not give a price in advance, because the amount of opening needed depends on what is found. The crew explains the work before it starts, and the decisions are the homeowner's.
Who repairs the leak once it is found?
A licensed plumber repairs the supply or drain line. The water-damage crew records the leak and dries the area around it, and the two work from the same record.
The repair of the line is a plumbing job, and the plumber should give a written account of the repair and its location. The water-damage crew does not repair the line, and it does not decide how the plumbing is to be replaced.
The record of the leak, the readings, the photographs and the plumber's invoice are kept together. That file is what the insurer asks for if the leak is claimed.