Knowledge Is Prevention: Understanding Sprinkler Failures

Being equipped to recognize and respond to sprinkler failures is not only a key safety measure, but also a responsibility tied to compliance and the well-being of your environment and community. In our two previous blogs, we explored the field service testing process and essential sampling procedures—both of which are key components in understanding and addressing sprinkler failure. Together, they detailed key testing intervals, some floor-level inspection protocols, and the essential steps needed to properly test your sprinklers. NFPA 25 mandates that sprinklers be either replaced or tested based on their set intervals. For sprinklers to remain in service at these set intervals, compliance requires that they undergo proper testing. After completing your floor-level inspections, checking for signs of damage, and submitting your sprinkler samples, the next step is reviewing your test results. In this third segment of our four-part sprinkler testing series, we’ll dive into what it means when a sprinkler fails—and what actions need to follow.

The sprinkler testing process involves a variety of factors, which we discussed in part 1 of our blog series, Navigating the Requirements of the Field Service Testing Process. Once Dyne receives your sprinkler samples, they are placed into an oven to measure their response time index (RTI) as well as waterway clearance at 7 psi, ultimately determining whether the sprinklers pass or fail. According to Dyne Fire Protection Labs, an NFPA Global Solutions company, 5.4% of sprinklers tested to date have failed. Breaking down this failure rate, we find the following:

• 0.8% failed to activate at all
• 2.0% activated too late
• 4.5% activated but failed to release properly

Failures where sprinklers fail to activate can occur for several reasons. The most common causes include age-related loss of fluid, loading, or corrosion of the release mechanism. This is the most critical failure, as no water would be dispersed, and the sprinkler would be considered impaired. When a sprinkler activates too late, it still functions, but not as it was designed. While water will still be dispersed, it may not be at the response time needed for effective suppression. The most common failure, however, occurs when the sprinkler activates but the water seal fails to release properly. In this case, the water seal remains in place even after the release mechanism is activated. Ideally, the release mechanism should clear the path for water, but if the water seal is corroded or otherwise stuck in the water way, it prevents proper release.

Note: It's important to recognize that some sprinklers may fail due to a combination of these issues.

Although O-ring water seal sprinklers were first recalled in 2001 due to their high risk of failure, they continue to surface in the field. In 2024 alone, Dyne Fire Protection Labs found that 4% of the sprinklers submitted for testing still used this outdated design—resulting in a 54% failure rate. This serves as a serious reminder that if your system still contains sprinklers with O-ring water seals, that they should be identified and replaced as soon as possible to make sure your system functions properly when it’s needed most.

When we begin to digest this kind of data it is important to see how it impacts real-world outcomes. Stories like the one from Plymouth, Minnesota highlight exactly why functional sprinkler systems are so critical. In a three-story skilled nursing facility housing 65 residents, a single sprinkler head activated during a closet fire in a room with two bed-bound patients. That one sprinkler controlled the blaze until firefighters arrived and fully extinguished it—ultimately preventing what could have been a tragic outcome. This incident underscores the life-saving potential of properly maintained and tested sprinkler systems. It also reinforces the need for strict adherence to NFPA 25 standards to verify your system will perform when it matters most. A failed sprinkler can be the difference between a contained event and a devastating loss.

What happens if my sprinkler fails?

If a sprinkler fails to activate or fully release, NFPA 25 requires that all sprinklers within the defined sample area be replaced. It’s important to remember that the sample area is the specific section you designated for testing. For example, if your sample area encompasses the entire building, then all sprinklers throughout the building must be replaced. However, if you defined a smaller section—such as just the warehouse—as your sample area, then only the sprinklers within that space need to be replaced. This is why clearly defining your sample area from the start is a critical part of the overall sprinkler testing process.

This requirement introduces an important cost-benefit consideration when establishing your sample areas. While selecting the entire building as a single sample area might seem simpler, it also carries greater risk—because just one failed sprinkler could require full-system replacement. Conversely, dividing your facility into multiple, smaller sample areas can minimize financial exposure, limiting the scope of replacement to only the affected area. Being intentional about how your sample areas are defined is not only a strategic approach to managing costs, but also a smart way to reduce the potential impact of sprinkler failures and aid in long-term compliance with NFPA 25.

Every sprinkler tested by Dyne Fire Protection Labs comes with a detailed laboratory test report, which provides critical information about each sample’s performance and specifications. The report includes: 

• Job information 
• Year marking 
• Manufacturer 
• Series/Model/SIN 
• Temperature rating 
• Response type 
• Releasing mechanism 
• Water seal configuration 
• Measured response time 
• Response Time Index (RTI) 
• Water seal release results 
• Before and after testing photos are also available through a separate link

Note: These reports are available for viewing through Dyne’s website, offering full transparency into your test results, and helping you make informed decisions for system maintenance and compliance.

The data, the stories, and the requirements all point to one undeniable truth: knowledge truly is prevention. Understanding how and why sprinklers fail, adhering to NFPA 25 standards, and making informed decisions about your testing strategy can make the difference between mitigating a disaster or facing serious consequences. As our sprinkler testing series progresses, we’ll continue unpacking the critical elements that contribute to fire protection, compliance, and safety. Keep an eye out for the fourth and final segment!