Fire Hydrant Flow Calculator – Fire Flow & Flow Test (NBC / IS 9668)

The fire hydrant system provides manually operated fire fighting capability throughout the building. Every point in a building must be within reach of a hose, and each hydrant must deliver the required flow at the minimum operating pressure. This calculator determines hydrant spacing, total flow demand, and riserpipe sizing per NBC 2016 Part 4 and IS 9668.

NBC 2016 Part 4 specifies mandatory fire hydrant requirements by building height and occupancy. For buildings above 15 m: wet riser system mandatory (always-pressurised, water in pipes). For buildings above 30 m: dual-inlet connection for fire brigade pumper access. IS 9668 covers installation of fire hydrant systems. Breeching inlets (Siamese connections) at ground floor entry for fire brigade connection. Annual test: flow and pressure test at each landing valve.

A 20-storey building requires wet riser landing valves on every floor, with a design of 2 simultaneous streams for its risk category. Total flow demand Q = 2 × 900 LPM = 1800 LPM (30 L/s). Each landing valve must deliver 900 LPM at a minimum residual pressure of 3.5 bar. Checking coverage, hose reels (36 m effective radius) are spaced so no point on a typical 1200 m² floor plate is left uncovered, requiring roughly one reel per floor. The wet riser is sized at the minimum 100 mm (4") diameter, and the fire pump is selected to deliver 30 L/s at 3.5 bar plus pipe friction losses up to the topmost landing valve.