Liquid waste is a type of dirt that is often found in toilets. Detection of liquid waste such as water or urine in the restroom is challenging due to their limited physical appearances, e.g., transparency and small size. This paper proposes a new method to detect water droplets, including water splashes, on the toilet floor by using the heat absorption capacity of liquid. Water, air, and floor have different heat capacity characteristics. Increasing temperature difference between water droplets and surroundings is done using blowing air on the surface of the detection area. A thermal camera is used to observe the detection area and an adaptive threshold is implemented to localize water droplets. This study also proposed a low-cost calibration chessboard method for thermal images that can produce good contrast images for calibrating wide-angle thermal camera modules. The results obtained from the experiment were promising, the system was able to detect single water drop up to 2 mm in diameter on a floor of 90 × 170 cm, and detection rate was above 95% for water droplets with a minimal size of 5 mm in diameter.

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