Antifreeze Sprinkler System Requirements: A Guide to the NFPA 13 Update

antifreeze fire sprinkler system requirements

What is Antifreeze in Sprinkler Systems?

In fire sprinkler systems, antifreeze is a special liquid added to the water to stop it from freezing in cold environments. This is important because if water in a sprinkler system freezes, it can damage the pipes and prevent the system from working properly during a fire.

The antifreeze system uses a solution that lowers the freezing point of the water, ensuring the sprinklers can operate effectively even in freezing conditions. This type of system is a key part of fire protection systems in places where temperatures drop below the freezing point. Beyond preventing damage, having an antifreeze sprinkler system also means maintaining readiness in case of a fire. Properly functioning antifreeze sprinkler systems are necessary to safeguard buildings and people from the dangers of fire, particularly in colder climates.

Is Antifreeze Flammable?

Yes, antifreeze for fire sprinkler systems can be flammable under certain conditions.

The need to revise standards for antifreeze sprinkler systems arose from a significant event in 2009, where a fire highlighted the potential dangers of using certain antifreeze solutions in these systems. The National Fire Protection Association (NFPA) responded by updating its guidelines to enhance safety. These updates were important to make sure that antifreeze systems only use solutions that reduce the risk of exacerbating a fire.

Research by the Fire Protection Research Foundation discovered that certain concentrations of glycerin and propylene glycol could ignite when used in residential sprinklers. Specifically, propylene glycol solutions over 40% and glycerin solutions over 50% volume were found to be hazardous. These findings were based on numerous factors like the ignition source, type of sprinkler, and its location relative to the fire.

This comprehensive study led to a better understanding of how antifreeze for fire sprinkler systems behaves under fire conditions, resulting in stricter regulations. The research indicated that while lower concentrations behaved similarly to water, higher concentrations significantly increased the fire's intensity, suggesting a need for careful management of antifreeze levels in fire protection systems.

Antifreeze Sprinkler System Requirements Changes

Recent changes in the requirements for antifreeze sprinkler systems have significantly impacted how these systems are managed and maintained. Starting from the 2011 NFPA 25 edition, a new requirement was introduced mandating the use of listed antifreeze solutions in all antifreeze fire sprinkler systems.

The deadline set for this transition was September 30, 2022, giving manufacturers sufficient time to develop and distribute these safer, listed solutions. Now that this date has passed, virtually all antifreeze sprinkler systems must use these approved solutions to refill existing systems. These updates ensure that fire protection systems continue to operate safely without increasing fire risks, thereby safeguarding both property and lives. This change marks a significant step in improving the safety standards governing fire sprinkler installations across various environments.

New And Existing Fire Sprinkler System Requirements

Below is a summary of the types of antifreeze permitted to be used in new sprinkler systems when designed with NFPA 13, NFPA 13R, or NFPA 13D.

Design Standard Reference Listed Antifreeze Premixed Propylene Glycol with ESFR Sprinklers* Premixed Glycerine (<48% by vol) or
Propylene Glycol (<38% by vol)**
NFPA 13 8.6.2 X X
NFPA 13R 5.4.3 X
NFPA 13D 9.2 X

* Early suppression fast-response sprinklers should be listed for use with propylene glycol.
** Only to be used on piping supplying a specific area and when acceptable to the authority having jurisdiction.

Below is the outline of the permitted antifreeze solutions in existing sprinkler systems designed according to NFPA 13, NFPA 13D, and NFPA 13R and maintained according to the NFPA 25 or NFPA 13D.

Design Standard ITM Standard Reference in ITM Standard Listed Antifreeze Listed Antifreeze Outside of Listing Limitations* Premixed Propylene Glycol with ESFR Sprinklers Listed for Such Use Existing Glycerine (<38% by vol) or Propylene Glycol
(<30% by vol)**
Premixed Glycerine (<50% by vol) or Propylene Glycol (<40% by vol)
NFPA 13 NFPA 25 5.3.4 X X X X
NFPA 13R NFPA 25 5.3.4 X X X
NFPA 13D NFPA 13D 12.3.5 X

* Where used to replace nonlisted antifreeze solutions provided the temperature range limitations are not exceeded. The specific gravity and viscosity characteristics of the new antifreeze solution must be considered as to their potential impact on the system hydraulic calculations.
** Systems cannot be refilled with this solution. If solution fails to provide the needed freeze protection, it must be drained and replaced with a listed solution.

Listed Antifreeze Solutions for Fire Sprinkler Systems

What exactly does it mean for an antifreeze solution to be "listed"? When an antifreeze for fire sprinkler systems is described as listed, it means it has passed rigorous testing by a recognized certification agency, such as Underwriters Laboratories (UL). These tests ensure that the antifreeze meets strict safety and performance standards set for the fire protection system.

A listed antifreeze sprinkler system solution has been evaluated for several critical factors:

  • Solution stability to ensure it remains effective over time.
  • Viscosity, which affects how fluidly the antifreeze moves through the fire sprinkler system.
  • Electrical conductivity, which is crucial since it can influence corrosion within the system.
  • Compatibility with the materials used in the system, such as piping and seals, which ensures that the antifreeze does not damage these components.
  • Safety factors like toxicity and resistance to leakage, which are vital for ensuring the solution does not pose health risks or leak through the system.
  • Firefighting effectiveness, verifying that the solution aids in extinguishing fires efficiently.

In choosing an antifreeze fire sprinkler system, it is also important to know the listing limitations. These limitations might include the minimum use temperature, compatibility with system components, minimum design pressures, and specific volume limitations of the system. Following these guidelines is key to maintaining the system's integrity and effectiveness in preventing and fighting fires.

fire sprinkler system

Antifreeze Sprinkler System Testing Requirements

Here is a summary of the testing requirements for fire sprinkler systems designed and installed according to the NFPA 13 and NFPA 13R:

  1. Annual Testing: Test solution annually at the onset of the heating season.
  2. Determine Solution Type: Identify if the solution is:
    1. Listed antifreeze
    2. Premixed propylene glycol >30% for ESFR sprinklers
    3. Existing premixed propylene glycol <30% or glycerine <38%
  3. Sampling Locations: Take test samples from the top and bottom of the system, the most remote portion, and near the connection to the water supply.
  4. Additional Sampling: For every additional 100 gallons over 150 gallons of system capacity, take an extra sample.
  5. Testing Method: Use a hydrometer, refractometer, or follow manufacturer’s instructions to determine the specific gravity of test samples.
  6. Results Assessment: Check if the test samples are within the acceptable range.
    1. If Within Range: The solution can remain until the next annual test.
    2. If Not Within Range: Drain and refill the system with one of the acceptable solutions or use alternative methods for freeze protection.
    3. Unidentifiable/Unacceptable Solution: If the solution cannot be determined or is unacceptable, drain and refill as above.
  7. Alternative Freeze Protection: Options include converting to a dry or preaction system, or using listed heat tracing.

This is the summary of the testing requirements for fire sprinkler systems designed and installed according to the NFPA 13D:

  1. Annual Testing: Test antifreeze solution annually.
  2. Sample Collection: Collect two samples by either draining the system at the beginning and end of the drain or from ports at the top and bottom of the system.
  3. Determine Type and Specific Gravity: Identify the type of antifreeze and check specific gravity using a hydrometer or refractometer calibrated for antifreeze.
  4. Acceptable Samples: If samples are within the acceptable range and similar, and the solution is listed antifreeze, premixed glycerine < 50%, or premixed propylene glycol < 40%, the solution can remain until the next test.
  5. Unacceptable Samples: If the solution cannot be determined or samples are not within the acceptable range:
    1. Drain and refill with an acceptable solution (listed antifreeze, premixed glycerine < 50%, or premixed propylene glycol < 40%).
    2. Alternatively, convert to a dry or preaction system, or use listed heat tracing for freeze protection.


Substitutes to Antifreeze for Fire Sprinkler Systems

While antifreeze for fire sprinkler systems is commonly used to prevent freezing, there are alternative methods that can be used, especially where antifreeze use might pose safety concerns or where it is impractical; as noted in the 2016 NFPA 13 Standard Development.

Installing the Pipe in Warm Spaces

One effective method to prevent freezing without using antifreeze sprinkler system solutions is by installing the pipes in areas that are naturally warm or heated. This technique relies on ambient heat to keep the water in the fire sprinkler system from freezing, thereby eliminating the need for antifreeze.

Tenting Insulation Over the Piping

Another option is tenting insulation over the piping. This method involves covering the pipes with specially designed insulation materials to maintain the water temperature above freezing. This is particularly useful in areas where temperatures may drop significantly but controlled heating is available to protect the fire protection systems.

Listed Heat Tracing

Listed heat tracing involves using electrical heating elements that are applied along the pipes of a fire sprinkler system. These elements help maintain a constant temperature, thereby preventing the water inside from freezing. It's crucial that the heat tracing is listed, ensuring it meets safety standards appropriate for its use in antifreeze fire sprinkler systems.

Use of Dry Pipe Systems and Preaction Systems

Lastly, dry pipe systems and preaction systems offer robust alternatives to antifreeze sprinkler systems in freezing conditions. In these systems, the pipes are not filled with water until needed, which means there is no water in the pipes to freeze under normal circumstances. This method is highly effective in environments where the ambient temperature frequently drops below freezing.

FAQs on Antifreeze Sprinkler System

Do I need to put antifreeze in my sprinkler system?

You need to add antifreeze to your sprinkler system only if it is installed in an environment where the temperatures might drop below freezing, to prevent the water in the system from freezing, expanding, and potentially damaging the piping.

What is the antifreeze loop system?

The antifreeze loop system is a configuration within a fire sprinkler system where an antifreeze solution is used in specific sections of the system that are susceptible to freezing, ensuring that these areas remain functional during cold weather while the rest of the system operates with just water.

What antifreeze is NFPA approved?

NFPA-approved antifreeze solutions are those that have been tested and listed according to NFPA standards, such as solutions containing glycerin up to 48% by volume and propylene glycol up to 38% by volume, to ensure safety and effectiveness in fire sprinkler systems.

What is the purpose of the antifreeze?

The purpose of antifreeze in a fire sprinkler system is to lower the freezing point of the water within the system, preventing ice formation and ensuring that the system can operate effectively to suppress fires even in freezing conditions.

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The material provided in this article is for general information purposes only. It is not intended to replace professional/legal advice or substitute government regulations, industry standards, or other requirements specific to any business/activity. While we made sure to provide accurate and reliable information, we make no representation that the details or sources are up-to-date, complete or remain available. Readers should consult with an industrial safety expert, qualified professional, or attorney for any specific concerns and questions.


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Author: Herbert Post

Born in the Philadelphia area and raised in Houston by a family who was predominately employed in heavy manufacturing. Herb took a liking to factory processes and later safety compliance where he has spent the last 13 years facilitating best practices and teaching updated regulations. He is married with two children and a St Bernard named Jose. Herb is a self-described compliance geek. When he isn’t studying safety reports and regulatory interpretations he enjoys racquetball and watching his favorite football team, the Dallas Cowboys.