What are the risks if I run out of hot water?

If a large amount of hot water is used in a short period, the water heater won’t have enough time to reheat the incoming cold water.

When that happens, lukewarm water from the bottom of the tank can make its way to your taps, including the showerhead. This increases the risk of exposure to Legionnaires’ disease (legionellosis).

Note: The risk of Legionella increases as the water heater ages.

To learn more, read the answer to the question Is it possible to ensure that there is no risk of Legionnaires’ disease during Hilo peak demand events?