In a domestic hot water system (DHWS), segments that are stagnant for a day or longer will likely be?

In a domestic hot water system (DHWS), segments that are stagnant for a day or longer tend to be stagnant and cooler. When water is not actively flowing or being used, it can lose heat to the surrounding environment over time. The lack of circulation means that the water in these stagnant segments doesn't have a mechanism to maintain its temperature; instead, it will gradually cool down, especially if it is not adequately insulated.

Moreover, actively used segments, where hot water is flowing, will maintain a higher temperature due to ongoing heating from the water heater and the frequent exchange of water. Thus, in stagnant segments, the absence of heat input and circulation leads to a decrease in temperature, making them cooler compared to actively used portions of the system. This is particularly important to understand in the context of Legionella assessment and management, as cooler water temperatures can contribute to an environment where pathogens like Legionella can proliferate if they fall within favorable ranges.