This Danish Standard specifies a method for the enumeration of culturable microorganisms in hot domestic water by counting the colonies formed in low nutrient agar media after parallel aerobic incubations at 37 °C, 44 °C, 55 °C and 65 °C. The method is intended to reveal excessive bacterial growth in hot water tanks and tubes. By means of a low nutrient medium, a slightly alcaline pH, a range of incubation temperatures, and the pour-plate technique, the method is optimized to the needs of the bacteria present.