Why fire-main flow matters
SOLAS requires fire pumps and the fire main to supply enough water to the required number of jets at the required pressure. Officers often need a quick idea of how much water one 65 mm hose will throw, and whether two hoses will still leave enough pressure at the far hydrant. Flow depends on diameter and velocity. Velocity in a fire hose is commonly around 3 to 5 m/s if the pump can hold pressure.
How this calculator works
Flow = area × velocity. Area = π × (diameter/2)². The result is shown in litres per minute and cubic metres per hour. Multiply by the number of hoses for a total. This ignores friction loss, nozzle type and pump curve. Official capacity comes from the fire pump nameplate and the last pressure test of the fire main.
Who should use it
Useful during drills and for a first estimate when planning boundary cooling. Always follow the ship’s fire plan and the on-scene commander’s orders.