Wet Sprinkler System
In an underwater system, water in the pipelines is kept under pressure and feeds sprinkler heads activated by ambient heat. Only sprinklers exposed to high heat trigger to extinguish the fire. In most situations, this standard underwater system is highly recommended because it is reliable, easy to maintain, and relatively inexpensive. Since it is always pressurized and ready to operate, its response time is short. The main disadvantage of this system is water damage, which can be caused by accidental activations. These occurrences are very rare, but precautions can be taken to prevent them.
Dry sprinkler system
In an air under system, the pipeline network is constantly filled with pressurized air rather than water. It is held by a valve. When a sprinkler head is triggered, the pressurized air escapes from the pipeline. The valve opens, allowing water to flow through the pipes and then be ejected by the sprinkler. However, air under systems are prone to corrosion and scale buildup in the pipelines. These disadvantages are caused by condensation and residual humidity after required tests. This method is less reliable than underwater systems. Like pre-action systems, they are more complex (slower flow rate), more expensive, and more difficult to maintain. Air under systems are primarily used in spaces exposed to freezing temperatures.
The Pre-Action System
In a pre-action system, water is held by a valve, similar to an air under system. Opening this valve admits water into the piping and requires the activation of a local fire detection system. The system then functions like the standard underwater system.
Many establishments have opted for pre-action systems rather than underwater systems to reduce the risk of water damage caused by accidental activations, pipe leaks, or sprinkler heads. However, although using this system is indeed advantageous, it also has drawbacks and issues.
This type of system takes longer to reach its flow capacity, allowing the fire to spread in the interval and requiring the activation of a larger number of sprinkler heads, thus causing more water damage. Since pre-action systems are more complex than standard underwater systems, the risk of anomalies or defects increases accordingly. For example, a problem with the fire detection system could affect the proper functioning of the sprinkler system.
Due to their complexity, pre-action systems are more expensive to install and maintain than underwater systems.
Regardless of the type of sprinkler system chosen, it should always be designed by experienced professionals:
- manufactured by a reputable company, with high-quality materials;
- installed and tested in compliance with the requirements of NFPA 13 (Installation of Sprinkler System);
