Glossary Term
Fire Main
The fire main is the fixed water-distribution line that carries firefighting water from the yacht’s fire pumps to hydrants and hose stations around the vessel. In yacht use, the term normally includes the main pipe run, branches, isolating valves, hydrants, hose connections, and the arrangement that allows the required jets of water to be produced where a fire might occur.
Yacht code provisions make the function very direct. A fire main, water service pipes, and fire hydrants are to be fitted; the piping is to be sized for the maximum discharge rate of the connected pumps; and the construction is to resist heat, corrosion, and freezing. Where two pumps supply the fire main, the arrangement also has to allow isolation within the machinery space so that the second pump can continue feeding external hydrants during a machinery-space fire.
From an operational point of view, the fire main is only as useful as its valves, hydrant positions, hose reach, and actual pressure under load. Corrosion, poor modifications, dead legs, hidden freeze damage, and undocumented cross-connections can all weaken a system that looks fine on a drawing. That is why fire-main work usually belongs with pipework and plumbing and witnessed functional testing rather than with pipe replacement alone.