Two flush fire department connections with brass plates

Different parts of a fire department connection play a role in getting water to fire sprinkler or standpipe systems

Fire department connections (FDCs) ensure that certain fire sprinkler and standpipe systems can quickly get the water they need in an emergency. While some systems only need the FDC as a last resort, others require an external supply of water. Manual dry standpipe systems, for example, rely entirely on water pumped through an FDC for the water firefighters need.

In this article, we'll look at the role of a fire department connection in fire protection, and explain how different parts of a fire department connection – from swivels to signs –make the FDC's work possible.

If you already know everything you need to know, click here to browse our selection of fire department connections.

What are the parts of a fire department connection?

Most discussions of fire department connections focus on the inlet body, which contains all of the parts needed to connect a fire hose to pipes supplying a fire sprinkler or standpipe system. However, a complete and NFPA-compliant fire department connection features three parts, two of which are placed out of view:

  • The piping to the sprinkler system riser or main
  • A check valve, which prevents water from flowing in the wrong direction
  • The inlet body

The inlet body of a fire department connection consists of these parts:

  • Swivels, which connect fire hose to the FDC's inlets
  • The inlets, which facilitate water's entry into the FDC body
  • An outlet connecting the body to system piping
  • The body, which connects these components

Fire department connection components vary slightly across models. Some include clappers to direct the flow of water through the FDC and prevent water from exiting through open inlets. Fire department connections for Storz couplings may feature only the inlet and the outlet, providing a considerably more compact way to deliver a supply of water.

Most FDCs have a four-inch (4") or six-inch (6") outlet that connects to the building’s internal piping. That piping has either threaded ends – typically threaded with National Pipe Thread (NPT) – or grooved ends. Some have ends that are compatible with non-threaded Storz connections.

Open inlets have a tendency to gather dirt, dust, debris, and garbage, clogging system piping. For that reason, NFPA-compliant fire department connections also feature breakable caps or combination plug and chain assemblies that protect the FDC's inlets while the system is not in use.

What types of fire department connection are used today?

Three kinds of FDCs serve today's fire protection systems: exposed, freestanding, and flush.

Exposed FDCs are found on the outside wall of a building. The body, inlets, and swivels remain exposed for easy access by firefighters.

An exposed brass fire department connection with clogged inlets

This exposed two-way FDC has no caps, allowing debris to accumulate in the inlets.

Freestanding connections act as exposed FDCs but stand apart from the building being supplied. Freestanding FDCs connect to the building’s system through a buried pipe, creating a convenient point of access for firefighters.

A freestanding FDC with two swivels

A freestanding fire department connection in New York City. Source: Wikipedia.

Flush connections install flush to the building’s wall, leaving only the inlet couplings or swivels exposed. The body and outlets sit behind the wall, fully concealed by an identification plate. Flush FDCs are considered more aesthetically appealing, especially when the building requires three or more inlets.

A flush fire department connection with sign reading "sprinklers in garage only"

A flush fire department connection with two inlets. Source: Wikipedia.

Proper placement of fire department connections promotes immediate access for firefighters

An inaccessible or hard-to-find FDC can paralyze a fire sprinkler or standpipe system. As such, an FDC's location should always maximize accessibility for firefighters.

While local fire codes and the preferences of fire authorities govern the exact placement of an FDC, it should be positioned on the street side of the building and be easily recognizable. Each fire department connection should be positioned reasonably close to the nearest hydrant – 100 feet at most – but not so close that fire trucks or fire pumps placed near the hydrant lack clearance. Further, the engine and its hoses should not obstruct access to the building once connected to the FDC. Such obstructions can make it more difficult for firefighters entering or exiting the structure. Poorly-placed hose can also limit the positions available to firefighters who fight fires with aerial ladders.

Required signage identifies the system served by a fire department connection

NFPA-compliant FDCs require minimum signage that denotes the system they serve such as “Automatic Sprinklers,” “Standpipes,” “Standpipe & Auto-Sprinkler,” or “Test Connection.” Most manufacturers provide rings to clearly label these connections.

A round brass plate that reads "auto spkr standpipe"

The lettering on this identification plate indicates that an FDC serves a combination fire sprinkler and standpipe system.

These signs help first responders quickly locate the connection they need and know what they are connecting to. In addition, FDCs often feature signs that list the specific part or parts of the building that the fire sprinkler or standpipe system supplies.

Compatibility between the fire department's hose connections and a building's FDC couplings is paramount

The swivels on an FDC should always fit local fire hose couplings. Mismatched hose threads can delay firefighting efforts or render firefighters totally unable to supply water to a building's fire protection system.

One of the most common FDCs, known as a Siamese or two-way connection, has two 2 1/2-inch female swivel connections. NFPA requires that all fire department connections use 2 1/2" National Hose (NH) threaded female couplings unless the authority having jurisdiction designates another specific connection type.

A brass fire department connection with two inlet swivels

A two-way, or "Siamese," FDC.

The use of these female swivels distinguishes many FDCs from other connections, including roof manifolds and fire pump test connections, which feature male-threaded inlets.

Clappers guide water through fire department connections

Pressurized water moving through fire department connections can close built-in clappers. These clappers prevent water from exiting through open inlets. On an FDC with two or more inlets, clappers allow firefighters to add or remove hoses as needed. If the flow of water to one hose stops (or a hose bursts) a clapper will close to prevent backflow. In the meantime, other hoses can continue to supply water through the other inlets.

Standard two-way FDCs may include either one or two clappers. The clapper on a single-clapper model swings freely between both inlets. Water pressure from one inlet causes the clapper to block the unused inlet. When two hoses are used, the clapper takes a position between the two inlets, permitting the passage of water through both inlets. These models use less material and are generally more affordable.

A brass fire department connection, viewed from the outlet end. A hinged disc can be seen between the inlets.

Viewed through the outlet of a single-clapper FDC: a lone clapper rests between the two inlets, ready to swing closed as needed.

Double-clapper two-way fire department connections have one clapper for each inlet. While they are more expensive, double-clapper models offer added durability and an additional safeguard against bursting hose lines.

Water-based fire protection systems depend on fire department connections

Fire sprinkler systems rely on fire department connections for a supply of water when other sources are exhausted or unavailable. FDCs are also a key component for charging many standpipe systems. These systems are designed to provide water to servicing hoses in strategically placed locations inside a building or structure.

Standpipe systems are most common in large buildings, where areas of the facility are too far from an outside entrance, and multistory buildings, where they eliminate the need for running long lengths of hose in stairwells and on the ground. Manual wet standpipe systems require external charging from outside sources of water and thus rely on the fire department connection for both their water and their water pressure. In both cases, the FDC located at the ground level is the liaison between built-in piping and an external supply of water.

How to choose a fire department connection for your building

Before replacing an FDC, you want to check several things, including the number of female inlets, the number of clappers, and the thread type. If you’re replacing an FDC, the easiest way to do this is to purchase the same model. FDCs for NFPA-compliant systems should be selected and installed in accordance with local fire code along with NFPA 13: Standard for the Installation of Sprinkler Systems and NFPA 14: Standard for the Installation of Standpipe and Hose Systems.

QRFS offers durable fire department connection kits designed for use as flush or exposed FDCs. Our selection of brass and chrome-finished exposed FDCs includes two types: angled FDCs, which feature an outlet at a 90-degree vertical angle to the inlets, and straight FDCs, which place inlets and outlets at the same vertical angle. All of our angled exposed FDCs are perfect for use as freestanding fire department connections when coupled with a metal freestanding sleeve.

A chrome fire department connection with two inlets

This angled exposed FDC can be installed as a freestanding or exposed FDC.

Our selection also includes flush double-clapper, two-way fire department connections in brass or chrome, available with NYC or NST-threaded swivels.

QRFS makes it easy to add the signs, break caps, and plugs you need—simply browse for the FDC you want and select your accessories on the same page.

Browse all FDC Options and Accessories Here

This blog was originally posted by Jason Hugo and Cameron Sharp at on July 8, 2016. If this article helped you select the right check valve, check us out at or on Twitter @QuickResponseFS.