Jerry Naylis offers tips and recommendations for steps fire departments can take to prevent freeze-ups in pipes.
Training Notebook ❘ By GERARD J. NAYLIS Fire Sprinkler System Companies
Sprinkler pipes filled with water in a wet pipe-type sprinkler system are always subject to freezing when temperatures drop. National Fire Protection Association (NFPA) 13, Standard for the Installation of Sprinkler Systems, mandates that freeze protection be provided if anticipated temperatures fall below 40°F. Areas where a freeze-up may occur include the following:
Exterior walls in particular raise concerns in a few situations, including when the sprinkler pipe is in a concealed space such as a soffit or pipe chase or in cases of a loss of heat due to a malfunctioning, damaged, or out-of-service heating unit. Failure to properly drain a condensate valve (on a dry pipe sprinkler system) can also result in a freeze-up with subsequent broken piping and water discharge.
Freeze-ups can also be caused by cold air entering through cracks and loose siding along walls and in attic spaces. If the building’s envelope is compromised, cold air may enter. Additionally, unexpected drops in temperature can make some outdoor pipes targets for freeze-ups. Other causes of freeze-ups include cold snaps occurring during nights, weekends, and other idle periods. Freeze-ups can also take place when normally occupied areas are empty for a stretch of time during which a cold snap occurs.
Regardless of the reason, wet pipe sprinkler systems are likely to freeze when temperatures drop below 40°F.
(1) A condensate valve for a dry pipe sprinkler system concealed behind a decorative wall had no access panel to allow the valve to be drained. Moisture buildup over time reached the unheated area and froze during an unexpected cold spell over a weekend. An access panel and listing the condensate valve on the maintenance log would have prevented the freeze-up. (Photos by author.)
Preventing fire protection pipes from freezing temperatures is possible, and there are several ways to do it.
From a design perspective, one of the first options to try is to install a dry pipe sprinkler system instead of a wet pipe sprinkler system. Concerns over corrosion have prompted new technology that promotes nitrogen generators instead of the traditional air compressors that use ambient air to provide air pressure in the pipes.
The problem with traditional air compressors is the moisture in the ambient air. On entering the sprinkler pipe, moisture collects on the interior of the pipe and falls to the bottom. Over time, the water being exposed to the air in the pipe will cause corrosion. The result is leaking pipes that could cause the dry pipe valve to trip.
Ideally, with a dry pipe sprinkler, the nitrogen does not allow for corrosion. If dry pipe-type sprinkler systems are installed, these steps will help prevent a freeze-up:
2. Use antifreeze-type sprinklers in areas subject to freezing temperatures.
Following a fatal 2009 California fire involving an antifreeze-type sprinkler system, the NFPA amended NFPA 13 to require that only listed antifreeze solutions could be used. As of September 30, 2022, only listed antifreeze solutions can be used in antifreeze sprinkler systems. The upside: Antifreeze solutions work very well. The downside: Systems like this require a great deal of inspection, testing, and maintenance, all of which are much more expensive than standard wet pipe sprinkler systems.
3. Heat the space where the wet pipe sprinklers are located.
In theory, this sounds simple. However, making it happen is very difficult, particularly when you’re up against hidden spaces. Another consideration in the overall design and practicality of heating otherwise unconditioned or unoccupied spaces outside of the building’s thermal envelope is which energy conservation or similar codes apply in the jurisdiction.
As federal initiatives and mandates advance toward more energy-efficient building designs, fire protection design and pipe routing options may be affected. And while energy efficiency is not impossible to achieve, additional code requirements and design factors must be considered. The next few items in this list address energy efficiency.
(2) These wet pipe sprinklers were installed in an unheated, combustible, and concealed space in a newly built townhouse. The sprinkler pipe froze during the first cold spell and caused the sprinkler cap on one of the sprinklers to become dislodged. When the ice melted, the sprinkler discharged water for an extended period, resulting in more than $200,000 in water damage. The builder mistakenly believed that residual heat from a heating unit and ductwork would protect the sprinkler piping.
4. Cover the sprinkler pipe with insulation.
This is a great solution in some cases but it’s not a fully foolproof option. Here’s why: While insulating a water-filled pipe may allow the pipe to retain heat for longer, insulation also limits external heat from reaching inside the pipe. And, ultimately, the expansion of the water as it drops below 40°F can still cause the pipe to crack. Then, as temperatures rise above the freezing mark, the ice will melt and the cracked pipe will leak.
Insulation generally slows the transfer of heat energy in both directions. So, while it initially helps retain heat at the piping, it will also later prevent ambient heat in the space from reaching and rewarming that pipe. When the water-filled pipe temperature dips below 40°F, ambient heat in the space (think daytime sunlight warming an attic) will have a tougher time reaching the pipe.
The listed heat trace wires are wrapped around the sprinkler pipe. An electrical current runs through the heat trace wires, creating enough heat to keep the sprinkler pipe above the 40°F temperature stipulated in NFPA 13.
6. Keep the sprinkler pipe in a heated space.
Another recommendation is to keep the sprinkler pipe in a heated space and then have only a dry-type sprinkler penetrate the cold space. While this approach may work for some installations, it is not the solution for every application, particularly where the cold temperatures come through an exterior wall or cavity.
7. Install a preaction-type sprinkler system.
Preaction systems involve a two-step process. A preaction valve is installed. This only allows water into the sprinkler pipe if another type of detection device, such as a heat detector or smoke detector, activates. Even if the thermal responsive element of the sprinkler activates, water will only flow if the preaction valve is opened at the time of activation. At that time, it sends a signal for the preaction valve to open.
8. Install a low-temperature sensing device.
In areas where colder temperatures are to be expected, a low-temperature sensing device could make a world of difference. This alarm would be connected to the building’s fire alarm system and transmit a supervisory signal to warn that the temperature in the affected area is approaching the freezing mark. It indicates that corrective action is needed to introduce heat to the area to prevent a freezing situation.
With this approach, the location to which the low-temperature signal is sent (central monitoring station) must have clear instructions for notifying personnel who have the authority to take the corrective action. They will need to do so in a timely manner.
This is a relatively inexpensive strategy for preventing freeze-ups. Keep these two requirements in mind: (1) The low-temperature sensors must be placed throughout and in close proximity to the sprinkler piping. (It serves little value to have low-temperature sensors in a sprinklered attic space if the water-filled piping also runs up through an outside wall where it is subject to freezing but there are no low-temperature sensors). (2) once the low-temperature sensor activates and transmits the call to the designated responsible party, a plan must be in place for how to best direct or apply temporary emergency heat into the affected area.
Receiving notification of an impending freeze-up is useless without having a clear plan for next steps in place prior to such an event.
A freeze-up will likely not be discovered until temperatures begin to rise and the ice in the sprinkler pipe melts. When this happens, water will escape through the crack or break in the sprinkler pipe. If the flow is enough to trigger the water flow alarm, a signal should go to the fire alarm monitoring company, which, in turn, should transmit a water flow alarm to the fire department dispatch entity. This should trigger a response from the public fire department.
As with all water flow alarms, the arriving fire department units should ascertain the cause of the water flow alarm. If the department ran into smoke, the fire department would quickly recognize that the reason for the flow alarm was a fire being controlled by the building’s automatic sprinkler system. In this case, the supply hose should be stretched from one of the first-due engines to the fire department connection. The automatic sprinkler system should also be supplemented.
A firefighter equipped with a radio should be sent to the sprinkler system control valve and await instructions from the incident commander or operations officer. The firefighter at the sprinkler control valve should ensure that the sprinkler valve has not been shut by a well-intentioned employee who may have mistakenly assumed there was a broken pipe and wanted to prevent water damage, not knowing there was a fire.
Unfortunately, sprinkler control valves also could have been shut off by a person who started a fire and wanted to cause greater damage. In these cases, it is less likely that a water flow alarm would have been transmitted.
If there is no fire, the incident commander or operations officer should direct the automatic sprinkler control valve to be shut. The firefighter sent to the valve should shut it and stay there to await further orders. This will stop the flow of water to the sprinkler system. In the case of a broken pipe flowing water, opening the riser’s main drain will expedite removing water from the system to reduce water damage. It will also render the building unprotected. At this point, swift action from the fire department is necessary to protect and preserve the building.
1. NFPA 13, Automatic Sprinkler Systems Handbook, 2022 edition. National Fire Protection Association (Quincy, MA).
2. The Handbook of Property Conservation, 3rd edition, 1983. Factory Mutual System (Norwood, MA).
3. International Fire Code, 2015, 2018, and 2021 editions.
4. NFPA 1, Fire Code, National Fire Protection Association (Quincy, MA).
GERARD J. NAYLIS, ARM, CFI, is a lifelong member of the fire service as a certified firefighter, fire officer, fire inspector, fire official, and fire investigator with public fire departments. Additionally, he spent more than 15 years in the HPR property insurance field with FM Global and its legacy insurance company, Arkwright Mutual Insurance Co. He served more than two years with the U.S. Consumer Product Safety Commission as the eastern regional manager for field operations. He is currently in private practice, where he conducts loss examinations and evaluations, fire protection analysis, and code consulting.
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