As noted in a previous (January 2025) Underwriters’ Corner, wet pipe automatic sprinkler systems are preferred since there is no delay in delivering water onto a fire.

Anti-freeze systems were discussed as a good alternative to protect relatively small areas of a wet pipe sprinkler system exposed to temperatures 40°F or lower. However, there are cases where antifreeze loops could be of limited use, primarily in climates that experience very low temperatures.

The current NFPA 13 Standard requires listed antifreeze solutions. While very effective, they can only protect to certain low temperatures, in the range of -10°F to -25°F. There are many areas of the country that can experience these temperatures in the winter. Also, antifreeze systems require regular inspection, testing, and maintenance to be sure they function properly.

There are substitutes, recognized by NFPA as safe and effective for protecting areas of sprinkler piping exposed to very low temperatures. These are heat tracing systems and pipe insulation.

Insulation protection can be used where sprinkler mains or risers pass through open areas exposed to freezing. Heat tracing is discussed in the accompanying Underwriters’ Corner article.

by Nils Deacon, Manager, Inspections and Rating Services

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