Sprinkler System Types, Components, and Heads
Pick the system that matches the hazard
Wet pipe systems are the default: simple, fast, and reliable. Dry pipe systems use air or nitrogen above the valve and are used where freezing is a risk; on trip, the valve opens and water must travel to the remote head, so the code limits how long that may take (the familiar figure is 60 seconds for the valve to deliver water). Preaction systems require a detection signal before the valve opens and are used to protect sensitive spaces. Deluge systems open all heads at once through open nozzles for high-hazard discharge. Residential and ESFR heads are special-response devices with their own listing rules - never substitute one for a standard spray head.
Heads and components
Know pendent, upright, sidewall, concealed, and dry heads, and the temperature ratings: ordinary 135–170°F, intermediate 175–225°F, high 250–300°F, and progressively higher ranges above that, each with its own color coding. A head's K factor, response type (quick or standard), and listing drive where it may be used. Other components: alarm check valve, dry pipe valve, preaction valve, flow switch, inspector's test connection, main drain, and the waterflow alarm.
Traps
- Using an upright where a pendent is required, or vice versa (upright deflectors face up).
- Assuming a higher-temperature head solves a hot ceiling; it may not be listed for it.
- Forgetting that dry systems need auxiliary drains and slope.
Worked example
An unheated warehouse dock needs freeze protection but fast response: a dry pipe system with listed dry pendents through the wall into the heated space, sloped to a drum drip, with the dry valve and quick-opening device sized so water reaches the remote head within the code time limit.