Water Demand Calculator

Your details

Population-based suits community planning and early-stage design. Fixture-unit-based suits detailed plumbing design for a specific building.
Total occupants or design population served by the system.
people
Select the occupancy type; each has a recommended per-capita consumption rate.
Ratio of peak hourly flow to average hourly flow. Typically 2.0-3.0 for residential, 1.5-2.0 for commercial.
Landscaped area to irrigate. Set to 0 to skip irrigation demand.
m²
Typical landscape irrigation rate: 3-8 L/m²/day (0.07-0.20 gal/ft²/day).
L/m²/day
Percentage added for pipe losses and unaccounted-for water. WHO recommends 10-15% for well-maintained systems.
%
Required fire-fighting flow. Set to 0 to exclude. Typical residential: 570-1,135 L/min (150-300 GPM); commercial: 1,135-3,785 L/min (300-1,000 GPM).
L/min
Required fire-reserve duration. Typically 60-240 minutes depending on occupancy.
min
Days of average daily demand to store. Single-family homes: 1 day; hospitals and critical facilities: 3-7 days.
days
Applies a 25% reduction to model low-flow fixtures (WaterSense or equivalent standard). Useful for comparing standard vs. efficient scenarios.
Average daily demandModerate water loss
9,350

Total average daily water requirement including all components

Peak demand14.8
Domestic demand8,500
Irrigation demand0
Leakage allowance850
Fire reserve0
Required storage volume9.4
Efficiency saving2,125
Total fixture units0
Peak flow (GPM)3.9
Domestic8,500
Irrigation0
Leakage850
Efficiency saving2,125

Estimated average daily demand: 9350 L/day.

  • The peak demand of 14.8 L/min determines pipe sizing and pump selection for your service connection.
  • A storage volume of 9.3 m³ covers 1.00 day(s) of average demand plus any fire reserve.
  • Switching to water-efficient (WaterSense) fixtures could save approximately 2125 L/day, a 25% reduction in domestic consumption.

Next stepRefine your estimate using the fixture-unit method once your plumbing layout is known, as it gives a more accurate pipe-sizing demand.

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