The two main types of building fire sprinkler systems are wet-pipe and dry-pipe. Wet-pipe systems always have water in the pipes to the fire sprinkler heads, whereas the water only flows into dry-pipe systems when there is a fire.
Wet-pipe sprinkler systems have few components and should not be installed where they might freeze.
Guidelines
The National Fire Protection Association publishes NFPA 13, “Standard for Installation of Sprinkler Systems.” This publication tells how to design sprinkler systems for buildings and details the components that are acceptable to include in the systems. For example, only new sprinklers are allowed, and pipe, either ferrous or copper, must comply with specific American National Standards Institute (ANSI) and American Society for Testing and Materials (ASTM) standards.
Sprinklers
Sprinklers for residential systems come in six styles that provide different options for mounting them. Each style is available with ½- or 3/4-inch threads for attaching them to the water supply pipes. Some styles, called concealed, mount flush with the finished ceiling leaving only a small U-shaped copper piece exposed, while others completely protrude into the living space. A third style called flush is quite unobtrusive with only a small white dome visible when it is installed. Ceiling-mounted sprinklers are called pendants. Horizontal sidewall sprinklers mount to the wall near the ceiling and have deflectors that spread the spray out and down. Sprinklers come with different K-factors that help to match them to different locations in a room, and different places in a building, so they will emit enough water at enough pressure to extinguish a blaze.
