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Overhead and sump tank sizing from household demand.

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Quick Answer

The tank calculator sizes an overhead tank from the number of people at home. It starts at 135 litres per person per day, which IS 1172 allows for smaller city homes, and lets you pick up to 200 L, the top of the code's range for a big city with flush toilets.

Source: IS 1172, Code of Basic Requirements for Water Supply, Drainage and Sanitation (Bureau of Indian Standards), checked Oct 2026.

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Water Tank Size Calculator

Size your overhead tank from household demand, using the IS 1172 figures.

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About our water calculators

A house's water storage gets sized once and lived with for decades. Undersize the tank and you run dry every summer; oversize it and you pay for dead storage and stale water. The tank calculator sizes storage from your household's demand, using the IS 1172 litres per head for your size of town, and shows the working.

Size a tank from your householdPeople in the house, times 135 litres a day each, times days of storage, rounded up to the next tank size; a family of four with two days needs 1,080 litres, so a 1,500 litre tank.1People who live in the house2× 135 L each a dayIS 1172 range: 135 to 200 L3× days of storage4Round up to the next tank sizeFour people, 2 days: 1,080 L, so 1,500 L
Size a tank from your household. The water tank calculator does this arithmetic and shows the working.