Thermal imaging uses an infrared camera to read the surface temperature of walls, ceilings and floors. Wet materials cool as moisture evaporates, and a leaking hot line warms whatever sits above it. Those temperature differences show up on the camera’s screen as patterns that can be followed back toward the source.
What an infrared camera actually sees
A thermal camera doesn’t see water. It sees heat.
Every surface gives off infrared energy, and the camera turns that into a color map. Cooler areas usually show as blue or purple, warmer ones as yellow or orange. Damp drywall reads cooler than the dry wall around it because evaporation pulls heat out of it. A hot water line leaking under tile reads warmer because the water is heating the floor.
So a blue streak running down from a shower valve on the screen shows a temperature difference. The cause still has to be worked out. It might be water from a supply line, a cold pipe behind the drywall, a draft from a gap in the insulation, or a spot where the AC blows across the wall.
Where thermal imaging works best
- Hot line slab leaks. A leak on a hot water line under a slab warms the floor above it.
- Shower pans and valves. The cool pattern of wet material often spreads out and down from the source.
- Ceiling leaks under bathrooms. The camera shows how far moisture has traveled, which is usually wider than the stain.
- Wet walls with no visible stain. Moisture can sit inside drywall for a while, and a scan can pick up the cooler area before a stain shows.
What it can’t do on its own
A thermal camera tells you where a surface is warmer or cooler. It can’t tell you why on its own, and it can’t see deep into a slab, a thick wall or the ground. It can’t see through walls either: it reads the temperature of the wall’s surface, not the pipe behind it.
Cold water leaks are harder too. The water is often close to room temperature, so the only signal is the cooling from evaporation, which can be faint. That’s why a thermal image is a fast way to see where moisture is spreading and where to look next, rather than a way to pinpoint a leak by itself.
Conditions that affect a scan
- Time of day and sun. Afternoon sun heats west-facing walls, and stucco can stay warm well into the evening, which can mask a cool, damp patch.
- Air conditioning. Supply vents blowing across a wall or ceiling create cool patterns that look a lot like moisture.
- Recent showers. A recent shower leaves bathroom walls warm and damp on the surface.
Is it safe?
Yes. The camera only reads infrared energy that surfaces already give off. It doesn’t send out any heat or radiation, and nothing touches the wall.
Seeing a stain or a damp wall? See our leak detection services or tell us what you’re seeing.
