The type of sprinkler system that best suits your commercial property should be determined by your operations, building characteristics and fire protection needs. Wet pipe sprinkler systems, which store water in their pipes for distribution during a fire, are the most commonly utilized systems. Alternatively, some buildings (typically those located in areas where the pipes cannot remain at temperatures above 40 degrees Fahrenheit) use dry pipe sprinkler systems, which hold pressurized air or nitrogen in their pipes that—once released—open a valve and distribute water from the risers.
Pre-action sprinkler systems, on the other hand, combine elements of both wet and dry pipe systems—with the added component of a fire detection device. Such a system starts with no water in its pipes, relying on a valve to open and permit water to enter the pipes after a heat or smoke detector signals that a fire is occurring. Once the pipes are filled, this water gets released as soon as the sprinkler heads are also able to detect the fire. In other words, two separate events must happen for a pre-action system to disperse water—both a detection device and the sprinkler heads must register a fire.
Pre-action sprinkler systems can be beneficial in water-sensitive environments, minimizing accidental discharge. Yet, these systems also come with several ramifications to consider. Review this guidance for more information on how pre-action sprinkler systems work, as well as the advantages and disadvantages of these systems.
Pre-action Sprinkler Systems Explained
Similar to dry pipe systems, pre-action sprinkler systems don’t initially contain water in their pipes. Water distribution in such systems is controlled by an electronically operated valve—also called a pre-action valve. In order to activate a pre-action sprinkler system, a heat or smoke detector must first indicate the presence of a fire. From there, the pre-action valve will open and allow water to fill the system’s pipes. The system will then function like a wet pipe sprinkler system, distributing this water from the pipes once the sprinkler heads are triggered by the fire.
There are two types of pre-action sprinkler systems:
- Single interlock—These systems operate as previously described, in which the pipes fill with water after a detection device signals a fire. Water distribution occurs when the sprinkler heads activate. If the sprinkler heads register the fire before the detection device, an alarm will go off, but water won’t be released without the device’s signal.
- Double interlock—These systems require both a detection device and the sprinkler heads to indicate the presence of a fire before even filling the pipes with water. Once both of these instances occur, water will enter the pipes and distribution to the sprinkler heads will happen shortly thereafter.
In both cases, pre-action sprinkler systems differ from wet and dry pipe systems in that they require additional fire detection steps—as opposed to solely sprinkler head activation—prior to the onset of water dispersal.
Advantages of Pre-action Sprinkler Systems
The primary advantage of a pre-action sprinkler system is that its multistep activation method significantly reduces the risk of accidental system discharge or unintentional water dispersal incidents. While this may not seem overly beneficial to some organizations, pre-action sprinkler systems are particularly advantageous in commercial properties with contents that are more susceptible to water damage. These might include:
- Buildings with perishable food stored in large-scale commercial freezers and refrigerators
- Museums, warehouses, galleries or retail stores containing high-value items (e.g., fine art, jewelry, musical instruments, electronics or historical artifacts)
- Libraries or other institutions holding specialty books (e.g., rare or collectible series)
- Research facilities or laboratories with advanced software (e.g., smart devices or scientific instruments)
In these environments, accidental sprinkler system discharge could result in costly, irreversible property damage. As such, implementing a pre-action sprinkler system can help increase the likelihood that the system will only activate and distribute water throughout the building when absolutely necessary—prioritizing fire protection and the preservation of water-sensitive items.
Disadvantages of Pre-action Sprinkler Systems
Despite the benefits that pre-action sprinkler systems can offer, these systems have several disadvantages as well. Specifically, pre-action systems can carry the following consequences:
- Added expenses—Because pre-action sprinkler systems consist of additional components, such as a heat or smoke detector and electronically operated valve, these systems are often costlier and more complicated to install than other sprinkler systems. Further, National Fire Protection Association (NFPA) standards—namely, NFPA 25—require commercial property owners with pre-action sprinkler systems to adhere to more frequent service intervals for various system components, ultimately compounding long-term expenses.
- Decreased reliability—Seeing as pre-action sprinkler systems rely on extra components to be fully operational, lacking a proper inspection and maintenance routine presents a heightened opportunity for individual components to fail—thus decreasing the functionality and overall reliability of the entire system. That being said, these systems require diligent maintenance and continued upkeep to ensure every component is working effectively.
- System limitations—Pre-action sprinkler systems also come with certain size limitations and minimal modification capabilities. With this in mind, if any operational changes or building renovations at a commercial property require significant sprinkler system adjustments, a pre-action system could be increasingly difficult to modify.
Lastly, it’s important to note that while pre-action sprinkler systems minimize the threat of inadvertent discharge incidents through two-step activation, this means that such a system will be slightly slower in its overall reaction speed during an actual fire. And in the event of a severe fire, even a minor delay in water dispersal—such as a couple seconds—can lead to increased property damage or loss of life.
Conclusion
Whether your commercial property already has a pre-action sprinkler system in place or you are thinking about having such a system installed in the future, make sure you understand the unique aspects of these systems—as well as how to properly maintain them. Being adequately informed about your property’s sprinkler system and what’s necessary to keep it in good condition can make all the difference in mitigating costly losses from a fire at your establishment.