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Fire Hydrant Demand Calculator

Work out fire hydrant demand instantly with clear inputs, formula shown and shareable results.

About Fire Hydrant Demand Calculator

Fire hydrant demand is the number of hydrants assumed to operate together multiplied by the flow each must deliver, and storage is that flow sustained for the required duration. Pressure at the landing valve is converted to head at 10.2 metres per bar, which is what the pump or tank height must provide.

Formulas

Fire water demand

L/min = hydrants x flow per hydrant; storage litres = flow x duration

Head

Metres = bar x 10.197

Worked example

With the default values below, Fire Hydrant Demand Calculator returns Total fire water demand of 1,800. Change any input above and every figure here is recalculated in your browser.

Inputs used

Hydrants assumed operatingminimum 1
2
Flow per hydrantminimum 1 L/min
900 L/min
Required durationminimum 1 min
60 min
Pressure required at the hydrantminimum 0.1 bar
3.5 bar

Results

Total fire water demand
1,800 L/min
Fire water storage required
108.00 m³
Storage in litres
108,000 L
Equivalent pressure head
35.7 m

Step by step

  1. 1Values used
  2. 2Fire water demand
  3. 3Head
  4. 4Total fire water demand= 1,800 L/min
  5. 5Fire water storage required= 108.00 m³
  6. 6Storage in litres= 108,000 L
  7. 7Equivalent pressure head= 35.7 m

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Fire water supply, storage and pump duty must be designed by a qualified fire protection engineer to the applicable code.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Fire water supply, storage and pump duty must be designed by a qualified fire protection engineer to the applicable code.

Frequently Asked Questions

How is the Fire Hydrant Demand figure worked out?

L/min = hydrants x flow per hydrant; storage litres = flow x duration. Fire hydrant demand is the number of hydrants assumed to operate together multiplied by the flow each must deliver, and storage is that flow sustained for the required duration.

How many hydrants operate at once?

Codes specify it by occupancy and building size, commonly two for a modest building and four or more for large industrial premises. It is a code requirement, not an engineering judgement.

What values do I need to enter?

This calculator takes 4 inputs: Hydrants assumed operating, Flow per hydrant, Required duration, Pressure required at the hydrant. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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