Antifreeze in sprinkler systems is used in spaces subject to freezing where the temperature cannot reliably be maintained at above which temperature?

• A. 32°F
• B. 28°F
• C. 40°F
• D. 50°F

Answer: (C)

Antifreeze is used in sprinkler piping to prevent freezing in spaces that may drop below a certain heating level. The practical threshold is 40°F—if the space cannot be reliably kept above 40°F, antifreeze is added to the system to lower the freezing point of the water and keep the pipes from freezing. The actual freezing point of water is 32°F, so relying on that would be too risky in unheated areas where heat loss and temperature swings occur. The other temperatures listed aren’t the trigger used in this context, because 40°F represents the defined limit above which regular operation is expected, and below which antifreeze becomes necessary.