Water Demand Calculator
A town of 100,000 people supplied at 135 lpcd needs 13.5 MLD on an average day, peaking at 2.5 times that.
CPHEEO: 135 lpcd for cities with sewerage, 150 for metros, 70 without sewerage.
13.5 MLD
- Peak factor
- 2.5
- Peak hourly flow (as daily rate)
- 33.75 MLD
- Average flow
- 156.25 L/s
Step-by-step solution
- Average = population × lpcd = 100000 × 135 L = 13.5 MLD
- Peak = 2.5 × average = 33.75 MLD
Water Demand Formula
Q = P × q / 10⁶ MLD
peak factor 3.0 (< 50,000), 2.5 (to 2 lakh), 2.0 (to 20 lakh), 1.8 (larger)
Worked Example
A town of 1,00,000 at 135 lpcd:
- Average = population × lpcd = 100000 × 135 L = 13.5 MLD
- Peak = 2.5 × average = 33.75 MLD
Peak hourly flow (as daily rate): 33.75 MLD · Average flow: 156.25 L/s
GATE tip
1 MLD = 11.574 L/s: keep this conversion handy when sizing pipes from a demand in MLD.
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Frequently asked questions
Where do the peak factors come from?
The CPHEEO manual sets them by population: smaller towns have sharper peaks because use is more synchronised.
How is fire demand estimated?
Kuichling gives Q = 3182√P L/min with P in thousands; CPHEEO suggests 100√P kL/day.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
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APA
Scientific Converters. (2026, October 15). Water Demand Calculator. Retrieved October 29, 2026, from https://scientificconverters.com/calculators/water-demand-calculator/
IEEE
Scientific Converters, "Water Demand Calculator," scientificconverters.com. Accessed: Oct. 29, 2026. [Online]. Available: https://scientificconverters.com/calculators/water-demand-calculator/