Wet pipe fire sprinkler systems are simple, but effective. They are filled with water under pressure, and when a fire causes one of the connected sprinkler heads to activate, water is immediately discharged from the activated sprinkler head. By a wide margin, wet pipe sprinkler systems are installed more often than all other types of fire sprinkler systems. Because of their simplicity and reliability, they generally require less installation and less maintenance than other types of fire sprinkler systems.
However, there are some situations in which wet pipe sprinkler systems might be ineffective. For instance, a wet pipe sprinkler system in a parking garage or other unheated building may be vulnerable to freezing. In regions using NFPA regulations, sprinkler system piping located in areas not maintained above 40°F should be protected against freezing. Learn about dry pipe sprinkler systems.