Massachusetts Plumbers Journeyman Practice Exam

What is the maximum temperature allowed for domestic hot water in residential buildings?

1. 110 degrees

2. 120 degrees

3. 130 degrees

4. 140 degrees

The correct answer is: 120 degrees

The maximum temperature allowed for domestic hot water in residential buildings is 120 degrees Fahrenheit. This standard is designed primarily for safety reasons, as higher water temperatures can lead to scalding injuries, especially in children and the elderly. Setting the limit at 120 degrees helps to reduce the risk of burns while still providing sufficient heat for typical household uses such as bathing, cooking, and cleaning. Moreover, maintaining hot water at this temperature helps in minimizing the growth of bacteria, such as Legionella, which can thrive in lukewarm water. Having the water temperature set at this level balances both safety and health considerations. Thus, ensuring hot water does not exceed 120 degrees is a crucial aspect of residential plumbing codes and practices.