#6 – Uncommon Fire Sprinkler System Malfunctions

Fears of unwanted fire sprinkler discharge persist, but such incidents are rare

Sprinkler-caused flooding can cause thousands or tens of thousands of dollars in damage. But these incidents are so rare, and fire sprinklers so well-made, that only 1 in 16 million fire sprinklers discharge from a manufacturing defect.

In this article, we take a look at why fire sprinklers can activate in the absence of a fire and talk about accidental fire sprinkler activation in commercial and residential systems. We also focus on the leading causes of accidental fire sprinkler activation and water damage, explaining how these incidents happen and how they can be avoided.

The components that make fire sprinkler heads reliable also render them vulnerable to unwanted activation

Fire sprinklers respond to heat. In our article “How a Fire Sprinkler Works: Thermal Sensitivity,” we detail how each sprinkler head has a heat-sensitive component, called a thermal element, that allows the head to activate at a given temperature. This thermal element is either a liquid-filled glass bulb designed to burst upon exposure to heat or a piece of soldered metal, called a fusible link, that melts off.

Side view of a fire sprinkler
The red glass bulb on this fire sprinkler head can break easily.

Even a small impact on these components can cause a fire sprinkler malfunction. In most fire sprinkler systems, breaking the thermal element causes the sprinkler head to release water just as it would in the presence of a fire.

In commercial buildings, preaction systems can address the threat of accidental fire sprinkler activation by design

Unlikely or not, all water-based fire sprinkler systems can cause water damage. But not all sprinkler systems are equally likely to discharge in the absence of a fire.

Most buildings have wet-pipe or dry-pipe fire sprinkler systems. In wet-pipe systems, the pipes supplying automatic fire sprinklers have water in them at all times. Pipes in dry-pipe fire sprinkler systems—used in environments subjected to near-freezing temperatures—have compressed air or nitrogen. But when the sprinkler head opens, water fills dry-pipe piping and discharges into the building. In both cases, water release quickly follows sprinkler head activation.

Preaction fire sprinkler systems, on the other hand, take extra steps to prevent unwanted discharge. Like dry-pipe systems, the pipes in preaction systems contain compressed gas. However, many preaction systems require two separate events before a fire sprinkler head can discharge: the activation of a sprinkler head and the separate detection of flame, heat, or smoke. Until then, water stays out of the pipes, meaning that a broken sprinkler head will release only compressed air.

Art galleries are often protected by preaction systems
An unwanted sprinkler activation could cause millions of dollars in damage in a space like this, making a preaction system especially desirable. Source: Wikipedia.

In settings where water damage could prove irreversible or especially costly, these systems can offer an additional measure of protection.

For a more in-depth look at fire sprinkler system types, click here.

Concerns about unwanted activation in residential fire sprinkler systems, while longstanding, have softened

While commercial and industrial buildings have long required fire sprinkler systems, mandates concerning residential fire sprinklers are relatively new—and often accompanied by a degree of anxiety. A 1977 survey indicated that roughly half of homeowners and occupants in single-family and multifamily residences did not want a residential sprinkler system in their home. Of those, 20 percent feared that the fire sprinkler system would cause unnecessary water damage.

A similar survey conducted almost two decades later showed that these beliefs remained largely unchanged. Three in every ten homeowners had heard about accidental fire sprinkler activations. A large share of those homeowners believed that sprinklers often activate accidentally.

In the last twenty years, those beliefs seem to have softened. A 2014 survey conducted on behalf of the Home Fire Sprinkler Coalition showed that nearly three-quarters of homeowners would be more likely to buy a home with sprinklers than one without them. Still, relatively few homes have these systems. As of 2016, only two states and a handful of cities had made residential fire sprinkler systems mandatory, despite recommendations from leading authorities in the field of fire prevention.

Fire sprinkler system malfunctions are uncommon and generally cause limited water damage

When a fire does break out, fire sprinklers greatly reduce both the water damage and the fire damage in most instances. For example, a fire sprinkler uses only 25 gallons per minute to control a home fire, whereas firefighters may use even ten times as much.

Firefighter with hose
Firefighters’ hoses move water at an impressive rate, making them ideal for tackling an out-of-control fire. But fire sprinklers can extinguish fires while they’re small, using far less water. Source: Free Stock Photos.

Compared to water damage incidents involving a building’s water supply or plumbing system, accidental fire sprinkler activations appear to be less costly and less frequent. Moreover, an unpublished analysis from the National Fire Protection Association (NFPA) estimates that at least half of reported non-fire sprinkler activations involve no water release by fire sprinkler heads. In most reported incidents, water simply moves into system piping or through a drain, causing a false alarm.

The same analysis notes that most malfunctions where water might be released involve a break or other damage to fire sprinkler system components. Leaks, freezing temperatures, and heat-caused incidents also contribute to unwanted activations, but not nearly as often. And non-fire activations of residential sprinkler heads are twenty times rarer than sprinkler activations involving an actual fire.

Accidental fire sprinkler activations have five primary causes

As we’ve mentioned, the chance of a sprinkler head expelling water in the absence of fire is extremely low. Manufacturers have adopted strict quality control procedures to ensure that fire sprinklers work as intended. Most jurisdictions allow only the use of tested and listed fire sprinkler heads. Finally, fire sprinkler installations and maintenance are left largely to licensed, bonded, and insured contractors who can design and assemble these systems in a way that minimizes the potential for error.

According to a 2012 study published by the American Society of Civil Engineers, most fire sprinkler malfunctions have one of five causes:

  • Overheating
  • Freezing
  • Corrosion
  • Mechanical damage
  • Deliberate sabotage


Nearly all fire sprinklers feature heat-sensitive parts that allow the sprinkler to activate as temperatures rise. But fire sprinklers can’t distinguish between different types of heat. If the temperature surrounding the head’s thermal element exceeds its activation temperature—whether that’s from steam, sunlight, fire, or another source—accidental fire sprinkler activation follows.

Portable heater
A building’s occupants may need to think twice before using portable heaters near fire sprinklers. Source: Your Best Digs via Flickr.

As a result, sprinklers installed in attics or near skylights must be selected with special care. If ceiling temperatures can exceed 155 degrees—the most common sprinkler activation temperature—then installers should choose a 200-degree or even a 286-degree head. Temporary sources of heat, such as space heaters or construction lighting, can also activate a sprinkler head.


Cold temperatures in under-insulated or under-heated buildings may deposit ice in fire sprinkler heads or piping. When the ice thaws, those components may crack, drip, break, or leak. At particularly high risk are the water-filled pipes found in wet-pipe fire sprinkler systems.

Common remedies include adding a listed anti-freeze solution to the pipes or increasing insulation around the system. When freezing temperatures cannot be avoided, dry-pipe fire sprinkler systems can provide an ice-resistant alternative.


Corrosion can build up over time and impact the functionality of the system or eat through the pipe. Surprisingly, dry-pipe fire sprinkler systems—which send water to sprinkler heads only when they activate—are far more prone to corrosion than other sprinkler system types. Trapped water in the pipes combines with humid air to quickly rust pipes from the inside out, causing fire sprinkler malfunctions. Many systems are now replacing air with nitrogen, as the absence of oxygen results in less corrosion.

A corroded dry pipe fire sprinkler main can lead to malfunction
A corroded fire sprinkler main can lead to malfunction. Source: Wikipedia with Creative Commons license.

Mechanical damage

Mechanical damage covers a variety of potential issues ranging from over-tightening of sprinkler heads to tapping the thermal element with a clothes hanger. As we’ve covered in our write-up on how to stop fire sprinkler discharge, the fragile, heat-sensitive components on a fire sprinkler can be damaged by fairly small impacts.

In many jurisdictions, fire code requires protective head guards for impact-prone fire sprinklers in commercial systems. But sprinkler heads in industrial facilities may face especially great risks from forklifts, construction crews, or other activity that places people or heavy equipment near sprinkler heads. In these instances, heavy-duty fire sprinkler head guards may help prevent accidental fire sprinkler activation.

Deliberate sabotage

While there’s plenty of interesting material on hoaxes and pranks-gone-wrong involving fire sprinklers, these incidents are fairly rare. Some environments, though, are especially prone to acts of vandalism. To prevent water damage, alternative fire sprinkler system designs may be needed in places like prisons, mental health facilities, and other locations subject to sabotage. Institutional sprinkler heads, which reduce access to the thermal element and other fragile sprinkler parts, may prove especially useful in such environments.

Choose high-quality fire sprinkler system components

While water damage worries homeowners, insurers, and building owners alike, accidental fire sprinkler activations are rare and largely avoidable. With a little common sense and healthy caution, most residential, commercial, and industrial fire sprinkler systems can provide decades of fire protection with no adverse consequences.

If you’re building or repairing a fire sprinkler system, take a look at the selection of residential and commercial fire sprinkler system components available at QRFS. Our stock includes a wide range of UL-listed and FM-approved fire sprinklers for buildings with fire hazards of all kinds. We have sprinkler heads, escutcheons, cover plates, head guards, and other accessories to meet a wide range of needs.

Click here to view our full selection of commercial and residential fire sprinklers and system components.

More questions about these rare fire sprinkler system malfunctions? Need help choosing a component that meets your building’s needs? Call us at +1 (888) 361-6662 or email support@qrfs.com.

This blog was originally posted at blog.qrfs.com. If this article helped you get a better sense of uncommon fire sprinkler head malfunctions, check us out at Facebook.com/QuickResponseFireSupply or on Twitter @QuickResponseFS.

4 thoughts on “#6 – Uncommon Fire Sprinkler System Malfunctions”

  1. A loud sound coming from spr I inkler system…sometimes every half hour. I hear it as a horn. Friends hear as jingling bells or like a house phone. Please advise what could cause this. Six months in my apt. Little or no help from management. Help !! I need some sleep. Thanks in advance.

    • Ringing bells might indicate the water flow alarm in a fire sprinkler system, meaning the system is activated/flowing water somewhere. Presumably, someone on premises would usually know that’s happening, as something would be getting wet. Otherwise, a horn, bell, etc. may be a fire alarm system, etc. You should call a fire protection pro—or better, compel management to do it—to figure out what’s going on! Best of luck resolving the situation!


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