Water Demand Calculator
Calculate average daily water demand and peak flow for a population from per-capita usage.
Estimates are for planning guidance only — always verify against local water-authority design standards and consult a qualified engineer before sizing mains, pumps, or storage.
How it works
- 1Enter the population served and the per-capita daily demand (typically 100–200 L/person/day).
- 2Set the peak factor — commonly 2–3× the average — for demand spikes.
- 3Read the average volume in m³/day, the average flow, and the peak flow for sizing mains and pumps.
Use cases
- Sizing water mains and service reservoirs for a new development.
- Checking whether a pump can meet peak demand for a growing community.
- Preliminary hydraulic design for small-town or rural water schemes.
Frequently asked questions
How is average daily demand calculated?
Average demand (L/day) = population × per-capita demand. 1000 people at 150 L/person/day is 150000 L/day (150 m³/day), an average flow of about 1.74 L/s.
What peak factor should I use?
A peak factor of 2–3× the average is common; 2.5× is a widely used default. Smaller populations need higher factors. Follow local water-authority guidelines.
Why only litres?
Per-capita standards are quoted in litres per person per day, so keeping outputs in L/s and m³/day avoids conversion errors in preliminary design.
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