NFPA 13 & 25: Sprinkler Systems
Automatic fire sprinklers are one of the most effective fire protections ever invented. NFPA 13 is the standard for designing and installing sprinkler systems, and NFPA 25 is the standard for inspecting, testing and maintaining them. This page explains the main ideas in plain language. It is not a substitute for the standards or for a licensed sprinkler contractor.
- Construction
- Facility Managers
- Fire Protection
How a sprinkler system works
- Sprinkler heads are connected to pipes filled with water (in a wet system) or with air or nitrogen (in a dry system). Each head has a heat-sensitive part, usually a glass bulb or a metal link.
- When a fire heats one head to its rated temperature, that head opens and sprays water. Heads operate individually, so only the heads near the fire go off, not the whole building.
- Flow in the pipes triggers an alarm that alerts people and the fire department.
- Systems are supplied through risers, control valves, a fire pump where needed, and a water supply.
Types of systems
| Type | Description | Used for |
|---|---|---|
| Wet pipe | Pipes always full of water | Most buildings in heated spaces |
| Dry pipe | Pipes hold pressurized air or nitrogen, and water enters when a head opens | Unheated areas where pipes could freeze, like parking garages, docks and warehouses |
| Pre-action | Needs two things to happen (a detector and a head opening) before water flows | Places where accidental discharge would be costly, such as data centers and museums |
| Deluge | All heads are open, and water flows from all when a detector trips | High-hazard places like fuel areas and aircraft hangars |
| Residential and NFPA 13R and 13D systems | Smaller systems for homes and low-rise residential buildings | One- and two-family homes (13D) and low-rise apartments (13R) |
Sprinkler head temperature ratings
Heads are rated to open at specific temperatures, and the liquid in glass bulbs is color-coded. Common ratings:
| Bulb color | Opens at about | Classification |
|---|---|---|
| Orange | 135°F | Ordinary (low end) |
| Red | 155°F | Ordinary |
| Yellow | 175°F | Intermediate |
| Green | 200°F | Intermediate |
| Blue | 286°F | High |
| Purple | 360°F | Extra high |
| Black | 440°F | Very extra high |
The right temperature rating depends on the ambient temperature where the head is. A head in a hot area, such as near a heater or in an attic, needs a higher rating. Use the right replacement head. Never swap heads without matching the type, temperature rating and orifice.
NFPA 13: design and installation
- NFPA 13 covers system types, hazard classifications (light, ordinary, extra and special hazards), water supply needs, head spacing and location, pipe sizing, hangers and bracing, seismic protection, valves and alarms.
- The design is based on what is in the building, how it is stored, ceiling height and construction. Changes in use, like adding high-piled storage, may require changes to the sprinklers.
- Sprinkler systems must be designed, installed and tested by qualified, often licensed, sprinkler contractors, with permits and inspections. See Building Permits & Inspections and Sprinkler Fitters.
- Systems must be hydrostatically tested and flushed before they are accepted.
NFPA 25: inspection, testing and maintenance
A system that isn’t maintained may not work when needed. NFPA 25 sets how often to check what. Typical schedules (check the current edition and your local fire code):
| How often | Examples |
|---|---|
| Weekly or monthly | Visual checks of control valves (open, sealed or locked, and supervised), gauges, and fire pump systems |
| Quarterly | Tests of alarm devices such as water flow alarms, and inspection of hangers, pipes and fittings |
| Annually | Visual inspection of sprinkler heads and pipes, main drain tests, tests of control valves and pumps, backflow preventers and fire department connections |
| Every 5 years and beyond | Internal inspection of pipes, checks of gauges, and testing of some valves. Sprinkler heads must be replaced or tested at intervals that depend on type and age (for example, fast-response heads at 20 years, and many standard heads at 50 years) |
- Qualified people do the work, and records must be kept. Building owners are responsible for making sure it happens.
- Deficiencies must be reported and corrected, and the fire department and insurer may need to be told.
Impairments: when the system is out of service
- A sprinkler impairment is any time all or part of a system is shut off or not working, for repairs, construction or a closed valve. During an impairment, the building is at greater risk. See Fire Alarm & Sprinkler Impairments.
- NFPA 25 calls for an impairment program: get a permit or tag, notify the fire department and insurer, notify occupants, limit the downtime, stop hot work, and restore the system as soon as possible. Provide fire watches or other measures if needed.
- Never leave a control valve closed after work. Tag it, and make sure it’s open and locked or sealed at the end of the day.
Rules for workers and building users
- Don’t hang or attach anything to sprinkler pipes or heads, such as lights, signs, wires, decorations, tools or clothes.
- Don’t paint, cover or coat sprinkler heads. Paint, dust and tape can prevent them from working. Replace a painted head. Cover heads only with the approved plastic caps during construction painting, and remove the caps afterward.
- Don’t hit or bump sprinkler heads with ladders, lifts, pallets or equipment. Damaged heads can leak or fail.
- Don’t store items too close. Keep a clear space below the heads, commonly at least 18 inches, as the code or the local fire marshal sets, so that water spray can spread. Don’t block heads with stacked materials, ducts or ceiling fixtures.
- Don’t shut off a control valve unless you are authorized, with an impairment procedure in place.
- Report leaking, corroded, damaged or painted heads, closed valves and anything hanging from the pipes.
- During construction, protect heads and keep the system working as it is installed in stages. See Jobsite Fire Prevention.
- Know where the main control valve and alarm panel are.
Other protections that work with sprinklers
Sprinklers work with fire alarms, smoke control, fire doors and extinguishers. They don’t replace evacuation plans. See NFPA 10: Portable Fire Extinguishers, Fire Alarm & Life Safety Technicians, Emergency Action Plans and Exit Routes.
Sprinkler system checklist
- System designed and installed by qualified contractors to NFPA 13 and local codes
- Inspection, testing and maintenance done on the NFPA 25 schedule, with records
- Control valves open and locked or sealed; alarms tested
- No painting, hanging or bumping of heads; 18 inches of clear space below or as required
- Impairments handled with permits, notices and fire watches, and ended quickly
- Changes in use or storage reviewed to see whether the sprinklers still protect it
Note: NFPA standards are copyrighted. This page summarizes them in general terms. Use the edition your jurisdiction has adopted.
Standards & references
Last updated: