Why are anti-freeze systems and loops on automatic sprinkler systems necessary?

May 11, 2022

by Nils Deacon, Manager, Inspections and Rating Services

Automatic fire sprinkler systems are the most effective element in protecting people and property from the disaster of structural fires. Wet pipe sprinkler systems are the preferred choice when possible. They are the most efficient in everyday applications.

Wet pipe characteristics are: The sprinkler piping is filled with pressurized water. When a sprinkler head operates, water immediately discharges. This gets water on the fire quickly and most efficiently. Wet pipe systems are less expensive to install, maintain, and service than dry pipe systems. Dry pipe systems are filled with pressurized air that is expelled when a fire activates a sprinkler head. There is a delay for dry pipe systems in the time it takes for water to reach the sprinkler heads controlling the fire.

Anti-freeze systems allow for the use of wet pipe systems in more buildings. When a small part of the system is exposed to freezing, anti-freeze loops are used. This would be in outside parking areas, balconies, and overhang areas of the building. The anti-freeze loop is filled with listed anti-freeze solution that is checked for stability as part of the annual inspection by a qualified sprinkler contractor.

DISCLAIMER: This information reflects the interpretation of MSO, Inc. with regard to NFPA Standards and Codes. It does not represent NFPA’s official position on the items discussed.

Anti-freeze exterior piping