The problem
Missing or mismatched plugs and swivels mean your Fire Department Connection (FDC) may not work in an emergency—and that can be catastrophic.
Firefighters rely on FDCs to hook up their hoses and supply water to standpipes and sprinkler systems. If a swivel is missing or the wrong type, they can’t connect. If a plug is missing or incorrect, debris could clog the system.
Ordering a replacement swivel or plug and realizing it doesn’t fit means you have the wrong thread type or size—either leaving your FDC absolutely impaired (no swivel) or at risk of getting blocked (no plug).
Why this matters
Not having the right FDC parts can lead to failed fire inspections and serious risks during an emergency. NFPA 25, the inspection, testing, and maintenance standard for standpipes and sprinkler systems, requires a 10-point quarterly inspection of FDCs that includes making sure:
- “Couplings or swivels are not damaged and rotate smoothly.”
- “Plugs or caps are in place and undamaged.” (Section 13.8.1, 2025 edition)
If swivels, which allow hoses to attach and rotate as hoses move, are missing or damaged, firefighters cannot connect to the FDC. If a plug is gone, debris may enter the FDC inlets and block water flow.
Both conditions are violations of fire protection codes and standards—meaning you’ll fail an inspection and face increased fire hazards.
The fix
Before ordering a replacement plug or swivel, you need to determine the exact thread size and type your FDC uses.
Measure correctly:
- Measure the inside waterway (hole) of the FDC opening with the swivel removed, not the wider measurement of the outside diameter of a swivel. You can also measure the narrower inside opening of a swivel, if you still have one.
- If you still have at least one plug, you can also measure the diameter of the inner threads, not the outer surface of the open swivel.
Know your thread type:
- Most US FDCs use 2-1/2” National Standard Thread/ National Hose Thread (NST or NH), or 1-1/2” NST for smaller systems—but not all of them!
- Some jurisdictions use unique sizes and threads. For example, FDCs in New York City may need 3” or 2-1/2” connections with New York Fire Department Hose Thread (NYFD). Others may require NPSH or even Storz threadless connections.
Swivels almost always connect to the FDC’s “snoot” via a groove if you choose the proper outer thread size. There are uncommon exceptions to this compatibility with older FDCs, however.
Best step: Call your local fire department or a fire protection contractor to confirm the correct thread standard and size for your FDC.
Buyer’s guide
Select a replacement plug or swivel only after identifying the FDC’s correct thread size and type. Always confirm with local fire authorities or a pro before purchasing to ensure compatibility.
Don’t guess—the wrong parts won’t fit and will leave your FDC out of compliance, or totally out of service.
Product recommendations
QRFS has the fire department connection parts you need
Check out our selection of:
If you need something that isn’t available online or have questions, please contact us.
FAQs
How do I measure the size of my FDC?
With a swivel removed, measure the inner waterway opening—the narrowest hole toward the back/inside of a swivel. If you still have one plug remaining, you can measure the diameter of the inner threads.
What’s the most common FDC thread type?
In the US, most commercial FDCs use 2-1/2” National Standard Thread (NST or NH), but sizes and the threads on specific systems and used by local jurisdictions may differ. Make sure to verify what you need!
What are some less common FDC threads?
Jurisdictions like New York City, San Francisco, and others may require different threads, such as NYFD or NPSH, or even Storz connections, the latter of which are threadless. Always confirm locally.
Who can help me identify the correct thread and size?
Contact your local fire department or a certified fire protection contractor—they can tell you precisely what your system requires. If you need something you don’t see at QRFS or require additional help, contact us!
