Fire Department Connection
The Lifeline
The FDC is the fire department's direct line into your fire protection system — when their pumper connects, they become your secondary water supply.
What Is a Fire Department Connection?
A Fire Department Connection (FDC) — historically called a "siamese" connection — is an exterior fitting that allows the fire department to pump supplemental water directly into a building's sprinkler system, standpipe system, or both. The FDC does not supply water on its own; it is a one-way intake point protected by a check valve that prevents system water from flowing back out NFPA 13, §8.17.
When a fire department engine connects to the FDC, it can boost system pressure and supplement the water supply, especially important when the fire has overwhelmed the building's primary supply or when the fire pump has failed. In standpipe systems, the FDC may be the sole water supply for hose connections on upper floors.
The FDC is required by NFPA 13 for most sprinkler systems and by NFPA 14 for all standpipe systems. Its location, visibility, and accessibility are critical — if the fire department cannot find or connect to the FDC quickly, the supplemental supply is worthless.
How the FDC Works
The operational sequence during a fire event:
Types of FDC Configurations
FDCs come in several physical configurations depending on building type, local fire department preference, and AHJ requirements NFPA 13, §8.17.2.
Wall-Mount (Flush)
Recessed into the building exterior wall. Most common in commercial buildings. Two or more 2½" female couplings with a check valve assembly behind the wall. Protected from vehicle damage.
Freestanding (Post)
Mounted on a standalone post or pedestal in the yard, away from the building. Used when the building is set back from the street or when the AHJ requires proximity to the fire lane.
Projecting (Exposed Siamese)
Traditional two-inlet "Y" fitting that projects from the building face. Visible and quick to identify. Common on older buildings and in dense urban environments.
Storz / Quick-Connect
Large-diameter single-inlet connection (typically 4" or 5") using a quarter-turn Storz coupling. Faster connection time. Increasingly required by modern fire departments.
Signage & System Identification
The FDC must be clearly marked so the fire department knows which system it feeds. Buildings may have separate FDCs for the sprinkler system and the standpipe system, or a single combined connection NFPA 13, §8.17.2.4.
Required Signage
- "AUTO SPKR" — serves the automatic sprinkler system only
- "STANDPIPE" — serves the standpipe system only
- "AUTO SPKR & STANDPIPE" — combined connection
- "DRY" or "PRE-ACTION" — identifies the system type where multiple exist
- Signs must be permanent, weather-resistant, and visible from the fire lane
- Many AHJs require the building address or system zone number on or near the FDC
Installation Requirements
NFPA 13 and local codes specify where and how the FDC must be installed. These requirements exist to ensure rapid, unobstructed access during an emergency NFPA 13, §8.17.2.
- Location: On the street side of the building, visible and accessible from the fire department access road
- Height: Inlets between 18" and 48" above grade (varies by AHJ — most prefer 36")
- Distance: Within 100 feet of a fire hydrant where possible
- Clear access: No landscaping, fencing, vehicles, or dumpsters blocking the FDC
- Check valve: Required between the FDC and the system to prevent backflow
- Drain: A ball drip or automatic drain between the check valve and the FDC inlets prevents freezing
- Caps: Each inlet must have a cap (breakable or threaded) to keep debris out
- Pipe size: FDC piping must match the size required by the system demand — minimum 4" for sprinkler systems
NFPA 25: FDC Inspection & Testing Schedule
Common Field Issues
FDC deficiencies are among the most frequently cited findings in fire inspections because the FDC is exposed to weather, vandalism, and neglect.
Missing or Damaged Caps
Caps prevent debris, insects, and trash from entering the piping. Missing caps allow obstructions that can block water flow when the fire department connects. Vandalism and weathering are the primary causes.
Obstructed Access
Landscaping grown over the FDC, vehicles parked in front, dumpsters blocking access, construction materials stacked nearby. The fire department has seconds, not minutes, to connect.
No Signage or Wrong Signage
FDC not labeled, labeled incorrectly (says "SPKR" but feeds standpipe), or signage faded beyond legibility. Firefighters connecting to the wrong system delays water delivery.
Leaking Check Valve
Water dripping from the FDC inlets indicates the check valve is not seating properly. This can also cause the ball drip to run continuously, wasting water and creating ice in winter.
Painted Over or Hidden
Renovation work sometimes covers the FDC with siding, stucco, or paint that blends it into the wall. The fire department cannot use what they cannot find.
Incompatible Couplings
FDC thread type must match the local fire department's hose couplings. NH (National Hose) thread is standard, but some older systems have non-standard threads. Storz adapters may be required.
Broken Ball Drip
The automatic drain between the check valve and inlets prevents trapped water from freezing and cracking the FDC body. A broken drip leads to ice damage in cold climates.
Interior Obstruction
Rocks, dirt, plastic bags, or even animal nests found inside FDC piping. Discovered during 5-year internal inspection or when fire department flow meets unexpected resistance.
Related System Components
The FDC is connected to and dependent on several other system components:
▶ Watch on YouTube
See sprinkler system inspections and maintenance on What The Fire Code.
Watch on YouTube →References
1. NFPA 13: Standard for the Installation of Sprinkler Systems, 2022 Edition, §8.17.
2. NFPA 14: Standard for the Installation of Standpipe and Hose Systems, 2019 Edition.
3. NFPA 25: Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, 2023 Edition, §13.8.
4. IFC 2024: International Fire Code, §912 Fire Department Connections.
5. NFPA Fire Protection Handbook, 21st Edition, Section 16.
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Discussion (2)
Great breakdown of the technical details. The NFPA 25 maintenance table is exactly what I needed for my ITM schedule.
Really clear explanation. Would love to see a companion video walkthrough of the inspection process.