By September 30, 2022, existing antifreeze solutions must be replaced by other means of freeze protection. This will undoubtedly mark the end of antifreeze in fire sprinkler systems. Designers must now clearly determine other options to continue protecting fire sprinkler systems in unheated spaces. Protecting the integrity of pipes in fire protection systems is particularly a challenge especially in regions that are subject to harsh winters. This includes structures or areas of buildings that are not climate controlled as water-filled pipes must remain above 40 F.
The issue is that propylene glycol and glycerin are flammable substances that can ignite at a high enough concentration. Indeed not all solutions combined are at proper proportions, and solutions that are do not always remain that way. Since water and the active ingredients have different densities (antifreeze is heavier), they naturally begin to separate over time due to gravity.
Antifreeze in Fire Sprinkler Systems
Antifreeze is commonly used in HVAC systems, automobiles, and combustible engines, and the principle is the same in a fire sprinkler system. A solution of a water and an active antifreeze ingredient is flooded into wet pipe systems to keep the water from freezing. Thus, when the proportion of the active ingredients near a sprinkler becomes too high relative to water, an antifreeze solution can actually serve as fuel for a fire when the sprinkler discharges.
Inspection & Maintenance Requirements for Sprinkler Systems Using Antifreeze
Fire sprinklers using antifreeze are subject to complex maintenance and inspection requirements. Until a listed non-combustible solution is introduced into the system, antifreeze solutions in existing systems must be tested annually and prior because of the onset of freezing weather.
If it is determined, based on records, tests or other reliable information that the solution found in the system is no longer permitted or if the type of anti-freeze cannot be reliably determined, the system must be drained and replaced with an acceptable factory premixed solution.
For a detailed summary of the current requirements for sprinkler systems containing antifreeze by the National Fire Protection Association can be found here.