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Automatic fire sprinkler systems are required by NBC 2016 Part 4 for buildings above 15m height, assembly occupancies, and hazardous storage. A properly designed system controls or extinguishes a fire at its earliest stage, protecting life and property. The design must ensure adequate pressure and flow at the most hydraulically remote sprinkler head — the most demanding point in the system.
IS 15105 is the Indian Standard for the design, installation and maintenance of automatic fire sprinkler systems, aligned with NFPA 13. Design densities per hazard classification: Light Hazard — 2.25 mm/min over 84 m² remote area; Ordinary Hazard Group 1 — 5 mm/min over 105 m²; Ordinary Hazard Group 2 — 7.5 mm/min over 126 m²; High Hazard — 10–20 mm/min over 260 m². These figures drive the pump flow and pressure requirements.
📐 Sprinkler Design Method (NFPA 13)
❓ Frequently Asked Questions
How many sprinkler heads are needed per floor in an office building?
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For ordinary hazard occupancy (offices): maximum coverage area per standard sprinkler head is 12 m². A 500 m² floor needs a minimum of 42 heads (500/12 = 41.7). Actual number depends on ceiling obstacles, obstructions, and the need for heads in enclosed spaces like storerooms. Each head must be within 2.3m of a wall and heads must be spaced with maximum 4.6m between heads.
What is the minimum water supply pressure for a sprinkler system?
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The minimum residual pressure at the most remote sprinkler head must be sufficient to deliver the design flow. For a standard K-80 head at 75 L/min design flow: P = (75/80)² = 0.88 bar (88 kPa). At the pump, add the system pressure loss in pipes, fittings, and the elevation difference. Typically, the pump discharge pressure is 7–10 bar for mid-rise buildings.
What is the difference between wet pipe and dry pipe sprinkler systems?
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Wet pipe systems keep pipes filled with pressurized water at all times — fastest response, simplest, most reliable. Used in all heated buildings. Dry pipe systems keep pipes filled with pressurized air/nitrogen; water enters only when a head opens. Used in unheated areas (parking decks, cold stores, atria in cold climates). Dry pipe systems have slower response — important for life safety calculations.
Does every room in a building need sprinklers?
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NBC 2016 and IS 15105 require sprinklers in all occupied areas. Exceptions (requiring fire engineer approval) include: electrical switch rooms, MV/HV panel rooms (use gaseous suppression instead), battery rooms, and small enclosures with fire-resistant construction. Toilets and bathrooms do not need sprinklers per NFPA 13 if the area is below 4.6 m² and has non-combustible fixtures.
How much water storage is needed for a sprinkler system?
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NBC Part 4 requires water storage for the design flow duration: Light Hazard — 30 minutes, Ordinary Hazard — 60 minutes, High Hazard — 90 minutes. For an ordinary hazard office floor at 650 L/min design flow: storage = 650 × 60 = 39,000 L = 39 KL. Add hydrant demand (typically 900–1800 L/min for 45–60 min) for total fire water reserve.
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