NFPA Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems (NFPA 25) Practice Exam

Stored water in fire protection systems must be maintained at a minimum temperature of 40°F to prevent freezing damage. This temperature is considered the threshold at which water will not freeze under typical conditions, thus ensuring that the fire protection system remains operable and effective during cold weather.

If the temperature were to fall below 40°F, there would be a risk of the water freezing, which could lead to blockages in pipes and valves, rendering the system ineffective in a fire emergency. Hence, maintaining water temperatures at or above this level is critical to ensure that the system functions properly when needed.

Other temperature options are either at the freezing point or lower than the minimum required temperature, which increases the risk of freezing and potentially compromises the system's reliability. Therefore, the chosen minimum of 40°F provides a safeguard against the adverse effects of low temperatures on the water supply of fire protection systems.