What’s Going On with Antifreeze in Fire Protection Systems?


By: Randy Conrad

Having been in the sprinkler fire protection industry for almost 40 years now, I have seen many changes as products and installation methods change and improve. One of the biggest changes in our industry would be the use of antifreeze but let’s step back before we move forward.

Antifreeze in Fire Sprinkler Systems

Since the beginning of sprinkler fire protection installations, the use of antifreeze solutions has been a viable means of protecting sprinkler systems from freeze-ups in cold weather areas. The concept is to fill the sprinkler piping normally filled with water with an antifreeze solution in the areas subject to freezing. A check valve separates the antifreeze portion of the sprinkler system from the water-based system. If a sprinkler is thermally activated, the antifreeze flows out the sprinkler head with plain water close behind to control the fire. 

For years this worked great, and as sprinkler fire protection became more popular and more buildings were required to have fire protection systems installed, antifreeze systems also became more prevalent. These systems were easy to install, were less expensive than the optional dry system, and required little maintenance. The only real maintenance item was to check the antifreeze solution annually to assure the concentration of antifreeze to water was still sufficient to prevent freeze-ups.  As time passed, many antifreeze system solutions became overcharged or contained too high of a percentage of antifreeze. In addition, both of the approved fire protection antifreeze solutions are combustible liquids.

Addressing Combustibility

In 2002 there was a report of a flash fire caused by a sprinkler system at a restaurant in New Jersey. It was an antifreeze system where a unit heater above a deck released a sprinkler head, and a flash fire occurred.  In 2010, multiple fires were reported in kitchens of apartment complexes where the sprinkler system accelerated the fire upon activation. In California in 2010, a cooking fire set off the sprinkler system, which caused a flash fire killing a woman and injuring others. This prompted action by NFPA, and in August of 2010, tentative interim amendments (TIAs) were issued prohibiting the use of antifreeze in any residential sprinkler systems.  In the next few years, several more TIAs were issued that get us to where we are today.

NFPA Guidelines

The 2016 edition of NFPA 13 limits the use of antifreeze to only solutions that are UL listed for fire protection use. This sounds like a logical decision; the only problem was that there were no antifreeze solutions listed on the market for fire protection use. This led to the next best option, which was to eliminate the process of recharging antifreeze systems and only installing factory premixed antifreeze.  This meant draining your entire antifreeze system and refilling it with a premix solution. This prevented over concentration but also limited freeze-up protection in most cases to -16F.

The 2017 edition of NFPA 25 stated that all existing antifreeze systems installed prior to September 20, 2012, shall not be required to use listed antifreeze until September 30, 2022. In 2020 the first listed fire protection antifreeze became available, and to date, there are three options. However, each of the new antifreeze solutions come with very stringent restrictions to their use. The new solutions require a backflow preventer and expansion chamber to be installed as part of the antifreeze system. The tricky part has to do with the required hydraulic calculations that are needed for both new and existing systems that will be using the new solutions. This is not just a one-for-one swap, old solution to new solution. Most scenarios will require some system re-piping and limitation to the temperatures the solution can be used in. There may be many situations where antifreeze is no longer an option and/or the cost of converting to a dry system is the most economical.

New antifreeze systems will not be going away but definitely reduced due to the new solution requirements. Existing antifreeze systems are good for now, but in less than a year (September 30, 2022), they will need to be converted to using the new listed solution, which may not be possible based on the listing requirements of the solution. Looking at options like converting your system to a dry system, heat tape, or heating the area, maybe the best answer.

For more information on the new NFPA antifreeze standards, contact Ahern today.

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