🚒 Fire Fighting

Fire Hydrant Calculator

Design fire hydrant systems for buildings. Calculate hydrant coverage, flow demand, pipe sizing, and hose reel requirements per NBC 2016 and IS 9668.

📐 Standard: NBC 2016 Part 4 / IS 9668
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ℹ️ About This Calculator

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.

📐 Hydrant System Design

NBC 2016 Part 4 / IS 9668

Hose Reel Coverage:
  Hose reel length = 30 m; jet reach = 6 m
  Effective coverage radius = 30 + 6 = 36 m per hose reel
  Place reels so every point is within 36 m of a reel

Landing Valve (Wet Riser) Coverage:
  Hose length = 15 m; jet reach = 10 m; effective radius = 25 m

Flow Demand:
  Each wet riser landing valve: 900 LPM (15 L/s) at 3.5 bar
  No. of simultaneous streams: depends on risk category (2–4 streams)
  Total Q = N_streams × 900 LPM

Pipe Sizing (Hazen-Williams):
  Wet riser: minimum 100 mm (4") diameter

❓ Frequently Asked Questions

What is the difference between a wet riser and a down-comer? +
Wet riser: permanently filled with water (pressurised), ready for immediate use. Water from pressurised fire pump system flows upward. Used for buildings ≥ 15 m. Down-comer: normally empty, gravity-fed from an overhead gravity tank, or used for fire brigade pumping from ground level. For modern buildings in India: wet riser is standard. Down-comers are rare in new construction.
How many hose reels are required per floor? +
One hose reel covers a 36 m radius (30 m hose + 6 m jet). For large open floors: provide one reel per 1300 m² (practical coverage area). Place hose reels near stairways and fire exits for easy access by occupants. Every point of the floor must be reachable – corners and dead-end corridors are critical to check. Minimum one hose reel per 900 m² of floor area in occupied buildings.
What pressure and flow is required at the topmost hydrant? +
NBC 2016: minimum 3.5 bar (35 m head) residual pressure at each landing valve when flowing 900 LPM through it. Static pressure (no flow): not less than 3.5 bar. Maximum static pressure: 7.0 bar at any hydrant point (install PRVs if exceeded). This ensures effective hand-held hose operation. The fire pump is sized to deliver this pressure after all pipe losses from pump to highest hydrant.
Does a building need both sprinklers and hydrants? +
NBC 2016 requires both systems for most buildings above 15 m: sprinklers for automatic fire suppression; hydrants for manual fire fighting by occupants and fire brigade. Sprinklers activate automatically and control the fire in its early stages. Hydrants provide sustained attack for larger fires or after sprinklers have controlled the initial fire. The systems can share a common fire pump as long as it is sized for the combined demand.
What marking and signage is required for hydrants? +
NBC 2016 and IS 9668: each landing valve cabinet must be red (RAL 3000 or equivalent), marked "FIRE", clearly visible and unobstructed. Hose reel location: illuminated sign. External fire brigade inlet: marked "FIRE BRIGADE INLET" with arrow. Monthly visual inspection required. Annual performance test. Quarterly pressure test (check gauge at each landing valve). Fire brigade access road must be marked on site plan.

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⚠️ Disclaimer: For preliminary engineering design only. Verify all results with a licensed engineer before use. Full disclaimer →

🚒 Fire Hydrant Calculator
Reference: NBC 2016 Part 4 / IS 9668