The Fire Department Connection, also commonly known as the siamese connection, is an important component found on most sprinkler and standpipe systems.
When a fire sprinkler system activates, the FDC provides a means for firefighters to connect hose lines to supplement the fire sprinkler system’s domestic water supply.
NFPA 13: Standard for the Installation of Sprinkler Systems is the industry benchmark for design and installation of automatic fire sprinkler systems, and component options.

The purpose of the FDC is to suplement the water supply, not necessarily provide the entire sprinkler system’s demand.

NFPA 14: Standard for the Installation of Standpipe and Hose Systems, provides requirements for the installation of standpipes and hose systems to ensure that systems will work as intended to deliver adequate and reliable water supplies in a fire emergency.