Keylion® 2 Way Siamese Connection
Commonly known as exterior FDC, this fire department siamese inlet serves as a backup water supply port to feed the building's fire pipeline system. We mount exposed models directly on exterior masonry walls, letting fire crews attach pump hoses quickly during emergency response.
One port of this dual inlet matches standard building standpipe piping, while the other end hooks up to fire hoses via brass couplings to feed spray nozzles. Operators only need to twist open the built-in valve to channel pressurized water toward fire suppression nozzles. Our siamese unit is forged from brass or cast iron , delivering polished corrosion-resistant surfaces and robust tensile strength to sustain long-term high-pressure service.
Technical Specification
| Category | Specification Detail |
| Product Name | Two-Way Siamese Fire Department Connection (FDC) |
| Type | Exposed Design (Wall Mount / Free Standing) |
| Marking on Escutcheon | AUTO. SPKR. FIRE DEPT. CONNECTION (Automatic Sprinkler) |
| Material | Heavy-duty Cast Brass / Forged Brass |
| Surface Finish | Polished Brass (Natural Finish) |
| Inlet Size & Type | 2 x 2.5" (65mm) Female Thread (NH / NST standard) |
| Outlet Size & Type | 4" (100mm) NPT Female Thread |
| Working Pressure | 300 PSI (2.1 MPa) |
| Test Pressure | 600 PSI (4.2 MPa) |
| Components | Double clappers to prevent backflow; 2 x Plug caps with chains; Round escutcheon plate |
| Application | Provides a supplemental water supply to the automatic sprinkler system by fire department pumpers. |
fAQ
Q:Why is the choice of 2.5" NST threads standard for most Siamese inlets?
The 2.5" NST (National Standard Thread), also known as NH thread, is the "universal language" of the US fire service. By standardizing these threads on the Siamese FDC, it ensures that any fire engine-regardless of its home municipality-can instantly couple its hoses to the building's system. Using non-standard or localized threads without an approved adapter is a major compliance risk that could lead to system failure during mutual-aid firefighting operations.
Q: Does a two-way FDC require an additional main check valve inside the building?
Yes. While the Siamese connection has internal clappers to manage the two inlets, a main system check valve must be installed in the piping before it joins the sprinkler or standpipe riser. This prevents the building's primary water supply (like a gravity tank or city main) from flowing backward out of the FDC inlets when the caps are removed. It's a fundamental "backflow" requirement that ensures system pressure is maintained at all times.
Q: How do the internal clapper valves function in a two-way FDC?
Most high-quality two-way Siamese connections utilize internal swing clappers. This is a clever mechanical design: if a firefighter only connects one hose initially, the water pressure from that single line forces the other clapper to seal shut. This prevents water from "short-circuiting" and spraying out of the unused inlet, ensuring all available pressure is directed into the building's fire protection system.
Hot Tags: 2 way siamese connection, China 2 way siamese connection manufacturers, suppliers, factory
