Best thermal cameras for moisture detection

What the camera needs to reveal: you cannot see water, only its effects

A thermal camera does not detect water as such. It shows differences in surface temperature, and water causes them in two ways. First, through evaporation: a damp area loses heat as it dries and looks colder than the dry wall around it. Second, through heat transport: a hot-water pipe warms the floor or wall along its route, and a hot-water leak creates a patch that spreads out from the leak point.

Thermography can therefore trace a heating network or underfloor heating, locate a leak in a buried pipe, map the extent of water ingress after water damage or find a waterproofing defect on a flat roof. It guides the investigation and avoids opening a wall in the wrong place. It does not replace a moisture measurement.

Getting the measurement conditions right

• Create thermal contrast: to trace a pipe, run hot water (or switch the heating on) a few minutes before measuring. The route appears gradually, then spreads: look early.
• Let evaporation work: a damp area shows up better in a heated, ventilated room where water is actively evaporating.
• Avoid stray heat sources: sun on a façade, a nearby radiator, furniture pushed against the wall or a work lamp distort the reading.
• Confirm every suspicion: a cold patch can also be a thermal bridge or a draught. A moisture meter, pin or capacitive, confirms dampness before any work.

For a detailed method, read can a thermal camera detect water leaks?

Distance, target size and resolution

The typical situation used by the selector is an area of about 10 cm seen from 2 m: a pipe route under tiles or the extent of a damp patch on a ceiling. Resolution demands are low here, because the areas you are looking for are large.

Example: with a 160 × 120 sensor and a field of view of about 36° (IFOV about 3.9 mrad), one pixel covers less than 8 mm at 2 m. The measurable area with our five-pixel margin is about 4 cm, well below the target. Even an 80 × 60 sensor remains usable to spot a patch. Resolution becomes useful, however, on large surfaces (flat roofs, a whole room of underfloor heating), where you are looking for the exact leak point in a wide view.

What matters, and what matters less

• Sensitivity (NETD): the main criterion. Evaporative cooling often produces only one or two degrees of difference, sometimes less. A NETD of 50 mK or better helps a lot.
• Manual temperature span: narrowing the palette to a few degrees brings out differences that an automatic span flattens.
• Overlay with the visible image: it helps locate the suspect area precisely on the wall or floor, and show it to a client or an insurer.
• Radiometric images and reporting: useful for a claim file or for monitoring drying over time.
• What matters less: high resolution, high temperature range and frame rate.

Common pitfalls

The first pitfall is taking every cold patch for moisture: a thermal bridge, a poorly insulated area or an air leak look the same. The second is about materials: glazed tiles or a varnished floor reflect their surroundings, and the displayed temperatures may belong to the ceiling or the operator. Change your angle to check. The third is looking too late: once hot water has spread through a screed, the patch widens and the leak point becomes hard to locate. Finally, a surface that looks dry can still be damp deeper down; only a suitable measurement confirms it.

Phone attachment or standalone camera?

To locate a leak at home, a smartphone module with good sensitivity works very well, since resolution is rarely the limit. For plumbers, leak-detection specialists and loss adjusters, a standalone camera is more practical day to day: instant use, ruggedness, visible overlay and reporting for the file. Some professional models also include or connect to a moisture meter. Both formats are ranked separately above.

What budget should you plan?

For an occasional need, the €€ band (€200 to €500) is enough; favour sensitivity over pixel count. For regular leak detection or claims work, the €€€ to €€€€ bands (€500 to €2,000) bring better sensitivity, visible overlay and reporting software. Beyond that, the extra cost mostly buys features this use rarely needs. See the price ranges page.

Frequently asked questions

Can a thermal camera see a leak behind a wall?

It does not see the water, only its effect on surface temperature: cooling through evaporation or warming from hot water. If the leak is old, cold or very deep, the surface difference may be too small to detect.

How do I trace underfloor heating?

Start the heating after a period off and watch the floor while it warms up. The pipes appear clearly at first, before the heat spreads through the whole screed.

Is the camera enough for an insurance claim?

It provides convincing images, but an assessor will also rely on moisture readings and on-site findings. A camera that records radiometric images and produces a report makes the file stronger.

Do I need high resolution to find a leak?

Rarely. Good sensitivity matters more for this use. The selector takes your distance and the size of the area you are looking for into account.