What is water leak detection and how does it work?
Short answer. Water leak detection is the process of finding hidden water from plumbing, HVAC or the roof using tools such as moisture meters, thermal cameras, acoustic listening gear, pressure tests and controlled water tests. Plumbing leaks are traced by plumbers or detection specialists, while roof leaks are traced by a roofer with an attic inspection and a hose test, and the cost depends on which kind of leak it is and how well hidden it is.
The tools pros use
- Moisture meters: pin or pinless meters read moisture in drywall, wood and decking and map how far water has spread.
- Thermal imaging: wet materials usually show up cooler on an infrared camera, which helps trace a ceiling stain back toward its source. The camera shows temperature, not water, so readings are confirmed with a meter.
- Acoustic and pressure testing: plumbers listen for leaks in pressurized lines and pressure test sections of pipe to find leaks in slabs and walls.
- Controlled water testing: for roofs and windows, wetting one area at a time with a hose while someone watches inside.
Roof or plumbing?
- The stain grows only when it rains: roof, flashing, windows or siding.
- The stain grows on dry days too: a supply line, drain, toilet seal, shower pan, or HVAC condensate line.
- The water meter moves with every fixture off: a supply leak somewhere in the house or yard.
- Summer only, below the attic air handler: a clogged condensate drain or overflowing pan, very common in Georgia attics.
What it costs
Plumbing leak detection is billed by the specialist and depends on how much testing is needed. Tracing a roof leak is usually part of a roofer's inspection, and many roofers do it free with an estimate. Ask up front whether any fee is credited toward the repair.
Related: common roof leak causes and what to expect at a roof inspection.