January 25, 2023

Anti-Freeze – Then and Now

Old man winter has settled in across the country for the next three months. With this change in season comes frigid temperatures and inclement weather. This drop in temperature creates obstacles for fire protection equipment, specifically, wet fire sprinklers in non-climate-controlled environments. In the past, wet systems in non-climate controlled spaces have been filled with antifreeze products to prevent a fire sprinkler pipe from freezing. As of September 2022, as per the National Fire Protection Association (NFPA), this is no longer a viable option. The following will explain further where the industry currently stands on the topic of antifreeze in wet fire sprinkler systems.


Starting with the basics, a wet fire sprinkler system is a sprinkler system that is always filled with water and is ready to control a fire upon activation of a sprinkler head. A wet sprinkler system must be maintained, at 40°F to prevent the sprinkler pipes from freezing. If any portion of the sprinkler system is located anywhere temperatures cannot be maintained at or above 40°F, other means of freeze protection is required. Alternatives for freeze protection include dry pipe sprinkler systems or antifreeze charged wet sprinkler systems to name a few.


An antifreeze sprinkler system is a sprinkler system where the pipes are filled with an antifreeze solution and upon activation of a sprinkler head, all the antifreeze solution is discharged, then water will follow to control a fire. Antifreeze is an adequate solution to preventing wet systems from freezing but does come with its own risks. With advances in antifreeze solution technology, there have been improvements on the premixed solutions, but prior to the introduction to the factory premixed antifreeze solutions, there have been incidents where antifreeze has made fires worse, due to excessive concentration of glycerin or propylene glycol in the antifreeze solutions. The National Fire Protection Association (NFPA) fire sprinkler standards describes the limitations associated with using antifreeze solutions in sprinkler systems. In 2009, there was a report of an incident in which an antifreeze solution that discharged from a sprinkler system may have ignited when exposed to a fire in a residential occupancy.



This leads us to the change in antifreeze requirements. When alerted to this potential public safety hazard, UL leveraged resources to assist NFPA to better understand whether certain concentrations of antifreeze in sprinkler systems could, in fact, contribute to a fire or create a hazardous condition when the solution was discharged. The research concluded that certain concentrations of antifreeze will intensify a fire.  Based upon the research, NFPA enacted emergency changes to its installation standards to prevent injury, loss of life and property damage. The current editions of NFPA 13, 13R and 13D generally require the use of listed antifreeze solutions for newly installed sprinkler systems. In addition, NFPA 25 requires that glycerin and propylene glycol antifreeze solutions currently used in installed sprinkler systems be replaced with a UL listed antifreeze solutions by September 30, 2022.


In establishing certification requirements for antifreeze solutions, UL addressed several potential concerns regarding the use of antifreeze beyond potential ignition. UL 2901 includes requirements for the solution that address its stability, effects when exposed to certain materials associated with sprinkler systems, human health and environmental impact, fire performance, hydraulic characteristics, and marking and installation specifications. Version 2 of UL 2901 published on November 15, 2018, included updates and revisions based on UL’s continued work with the test methods over the previous five years. Consistent with the current NFPA requirements, UL 2901 requires antifreeze solutions to be pre-mixed at the manufacturing site and they are not intended to be diluted or mixed in the field. In 2019, the first listed antifreeze was released.  There are now three listed antifreeze solutions on the market.  They can be used in CPVC and steel piping so this is certainly an improvement over the legacy antifreeze that can only be used in specific materials.  As of now, the listed antifreeze solutions can protect as low as -25 F.


Acceptable UL Listed Antifreeze Solutions

Currently, there are still only three acceptable UL Listed Antifreeze Solutions that can be used in antifreeze systems following the September 30, 2022 deadline as of 01/25/2023. Those acceptable solutions are:

  • Tyco LFP Antifreeze and Antifreeze+
  • Viking freezemaster™ Antifreeze from Lubrizol

These pre-mixed solutions are less than 30% propylene glycol or less than 38% glycerin and are permitted to remain in the sprinkler systems as per the new code requirement.


As stated above, by September 30, 2022, existing antifreeze solutions must be replaced by alternative means of freeze protection. This marks the end of antifreeze in fire sprinkler systems. Thus, designers must use alternative means to continue protecting fire sprinklers in unheated spaces.


The following are alternative means of freeze protection:


  • Insulate and apply heat to maintain spaces above 40 degrees Fahrenheit,
  • Install special scenario (dry) heads from a wet-pipe system,
  • Install a dry-pipe system,
  • Wrap pipe with listed heat trace, or
  • Use only UL listed pre-mixed antifreeze solution from the three available listed options.
  • A combination thereof.


Changes are common in the fire protection space and are usually a product of unwanted outcomes from an incident. The antifreeze topic in wet sprinklers is no different in the sense that what used to be a standard practice has resulted in either loss of life or property which brings us to the new change. As the technology evolves and advances in the fire protection arena, we must do the same and evolve with it. For more information on the new UL listed and NFPA approved anti-freeze solution on the market, contact either Tyco or Viking for more information. Tyco – Contact Us , Viking – contact us at techsvcs@vikingcorp.com or call 877-384-5464.




January 25, 2023

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