A sprinkler system consists of pipes along a ceiling that contain water under pressure, with an additional source of water for a constant flow. A sprinkler system consists of pipes along a ceiling that contain water under pressure, with an additional source of water for a constant flow. Attached to the pipes, automatic sprinklers are placed at select locations. When a fire occurs, a seal in the sprinkler head ruptures at a pre-established temperature, and a steady stream of water flows. Research compiled by Hall (2011) shows that sprinklers are an effective and reliable fire suppression strategy for buildings. However, he writes that sprinklers are still rare in most places where people are most exposed to fire, including educational buildings, stores and offices, public assembly properties, and especially homes, where most fire deaths occur. Hall notes that sprinklers are 87 percent effective. When a sprinkler system fails, the most frequent reason (65%) is that the system was turned off prior to the fire. Other reasons include manual intervention that defeated the system (16%), maintenance issues (7%), and inappropriate system for the type of fire (5%). A sprinkler system is a worthwhile investment for reducing fire losses. Lower insurance premiums actually can pay for the system over time. NFPA 13, Standard for the Installation of Sprinkler Systems, provides best practices for system design, installation, water supplies, and equipment. Also helpful as a “standard of care” and for protection in case of litigation is adhering to NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems. Failing to update inspection documentation with an insurer can affect coverage (Morton, 2011: 30). The AHJ may also be interested in such documentation. There are several kinds of automatic sprinkler systems. Two popular ones are the wet-pipe and the dry-pipe systems. With the wet-pipe system (Figure 13-4), water is in the pipes at all times and is released when heat ruptures the seal in the sprinkler head. This is the most common system and is applicable where freezing is no threat to its operation. Where freezing temperatures and broken pipes are a problem, the dry-pipe system is useful. Air pressure is maintained in the pipes until a sprinkler head ruptures. Then the air escapes, and water enters the pipes and exits through the opened sprinklers; because of this delay, dry-pipe systems are not as effective as wet-pipe systems during the early stages of a fire (Naffa, 2009: 28). Wet pipe sprinkler systems are the most common. In this system the sprinkler piping is constantly filled with water. When the temperature at the ceiling gets hot enough the glass bulb or fusible link in a sprinkler will break. Since the system is already filled with water, water is free to flow out of that sprinkler head. Contrary to what Hollywood would have you think, not all sprinkler heads will operate at once in this type of system. The temperature around that specific sprinkler head needs to be high enough to break the glass bulb or fusible link that is holding water back. Once that happens, water will immediately start flowing from only that head. Wet pipe sprinkler systems are the most reliable and cost effective. Therefore, they should be the first type considered when selecting a sprinkler system. However, there are times when a wet pipe sprinkler system may not be appropriate. One of the major factors in determining if a wet pipe system can be used is the temperature of the space to be protected. Will all areas of the building where the sprinkler piping is located be conditioned to at least 40OF (4OC) or greater? If the answer is yes, then there is no risk for the water in the piping to freeze and a wet system is the preferred method. However, if the answer is no, an additional study may need to be done to determine if an engineer can prove that although the temperature could drop below 40OF (4OC) it will never drop low enough for the water to freeze. If the temperature of the space cannot be guaranteed to eliminate the risk of freezing water, then a different system type should be chosen.
