Photo Courtesy of Liberty Mutual Insurance.
Impact of freezing temperatures on sprinkler pipe. This ice plug was found in a sprinkler system in a freezer however,
pipes in cold areas of an unheated building could produce similar results.
The issue of temperature frequently comes up in discussions about sprinklers and sprinkler systems. Here at NFPA, we receive a great deal of questions related to the exposure of sprinkler systems to potentially freezing temperatures. So, given the time of year and declining temperatures across the country, it seemed like a good time to get cozy with sprinkler freeze-prevention methods.
When water freezes, it expands and can cause damage to pipe and fittings, and yes even to sprinklers themselves. Over the years, the solution to the freezing problem has been to use a dry pipe system, a preaction system, or some combination of the two. The costs associated with installing a dry pipe or preaction system; however, can be prohibitive and the price tag for maintaining these systems can be equally daunting so be sure to fully understand the advantages, disadvantages and bottom line for these solutions.
Then there’s the option of heat tracing. This approach is not as simple as it may appear to be, and may not be the best protection method because of the need for insulating the pipe and electronic supervision of the power to the heating element.
In recent years, the environmental problems associated with anti-freeze systems have been well-documented. Since 2013, NFPA 13 has limited the use of anti-freeze solutions to listed solutions only. There have not been any pre-mixed or concentrate solutions for anti-freeze in fire protection piping listed - until recently. NFPA employees are not inclined to provide specific product or manufacturer recommendations; however, a quick search for “Listed Anti-freeze” on the UL web-site shows a product that is currently available and capable of protecting piping in cold climates - so anti-freeze is making a comeback!
Whatever product or solution you decide to use, it’s important to remember to closely follow the listing and manufacturer’s instructions. Guidelines vary from product to product and often times vary from previously accepted practices. Misusing a listed product can be as dangerous as using an unlisted product; so be sure to use the right option and apply the right knowledge for maximum benefit and safety.
For example, NFPA 13 requires the use of an expansion chamber when using anti-freeze in a sprinkler system because fluids expand and contract due to varying temperatures. Figure 18.104.22.168 of the standard illustrates the appropriate arrangement of the expansion chamber and a backflow preventer (where required); while the manufacturer’s instructions should be used to determine the size of the expansion chamber. There are limitations to using anti-freeze in a system. System volume and limitations on the classification of occupancy or sprinkler type need to be considered. When using these chemicals, it is critical that the manufacturer’s instructions and listing limitations be followed.
As meteorologists warn, “Baby, it’s cold outside” and water cooler conversations center around tumbling temperatures – keep in mind that frigid weather can have a brutal impact on sprinkler systems. Look at systems, solutions, and safety in totality to ensure that the refrain, “Baby, it’s cold outside” is not followed by “darn, it’s wet inside” due to pipes bursting or sprinkler systems malfunctioning!