Quick answer: Fire water storage is the sum of the hydrant demand and sprinkler demand held for the code-required duration. NBC Part 4 specifies storage by occupancy — e.g. large buildings commonly need 2,00,000 litres for hydrants plus additional sprinkler storage, sized so pumps can run for the mandated period (typically 60–90 minutes).
How fire storage is sized
The tank must supply the fire pumps at full duty for the required run time without refilling. NBC Part 4 and IS 15105 give the flow rates and durations for hydrant and sprinkler systems by building class.
Storage = (Hydrant flow × duration) + (Sprinkler flow × duration)
Example basis: hydrant 2280 LPM, sprinkler per hazard density
Duration: typically 60-90 min per NBC occupancy classWorked example
Hydrant demand 2280 LPM for 60 min = 1,36,800 L; sprinkler demand say 1500 LPM for 60 min = 90,000 L. Total fire storage ≈ 2,26,800 litres, rounded to a standard tank size. Confirm exact figures against NBC Part 4 for the occupancy.
Combined hydrant + sprinkler demand and total storage per NBC Part 4. Free tool.
Open the Fire Water Tank Calculator →Frequently Asked Questions
How much fire water storage is required as per NBC?
It depends on occupancy class. NBC Part 4 commonly requires around 2,00,000 litres for hydrant systems in large buildings, plus separate sprinkler storage, sized for 60-90 minutes of pump operation.
Is hydrant and sprinkler storage combined?
Total fire water storage is generally the sum of hydrant and sprinkler demands for the required duration, though some designs share storage where codes permit. Always follow NBC Part 4 for the specific building.