Why does a building need a fire department connection if it already has a city water supply?

Q: What does a jockey pump actually do in a fire-pump system?

The jockey pump is a small pressure-maintenance pump that tops the system pressure back up after a tiny leak or thermal drift, so the main fire pump does not short-cycle every time pressure dips. It runs on small drops; the main pump only starts on a real demand like an open sprinkler.

Q: When is a diesel fire pump required instead of an electric one?

NFPA 20 requires a non-electric driver — typically a diesel engine — when the building has no reliable second source of utility power and the occupancy classification demands it (high-rise, life-safety critical, large warehouse). The diesel engine has its own day tank, batteries, and weekly no-flow test routine.

Question

Why does a building need a fire department connection if it already has a city water supply?

Accepted Answer

An FDC is a parallel hose-thread inlet on the building exterior so the responding fire engine can pump pressurized water — or foam concentrate — directly into the standpipe or sprinkler system. NFPA 14 requires one on every standpipe system because the city main can fail, drop pressure under fire flow, or fall short of the riser demand on a high-rise. The engine becomes the supplemental pump.

Why does a building need a fire department connection if it already has a city water supply?

Answers