Water tank capacity calculator
Estimate the daily water need of a house from the number of people, and the smallest standard tank that holds one day of it.
How big a water tank does a house of 5 need?
A house of 5 people at 135 litres per person needs about 675 litres of water a day. The smallest standard tank that holds one day of that is 1,000 litres. A house of 8 needs about 1,080 litres a day, which fits a 2,000 litre tank. Enter your own numbers above.
How is it worked out?
Daily water need = number of people × litres per person per day. The calculator then picks the smallest tank from the common sizes (500, 1,000, 2,000, 5,000 litres) that holds one day of that need.
Which litres-per-person figure should I choose?
| Litres per person per day | Where it comes from | Common use |
|---|---|---|
| 135 | The figure IS 1172:1993 gives for lower-income housing, and the usual urban figure used by water-supply manuals | The default for a typical house |
| 150 | The lower end of the IS 1172:1993 range of 150 to 200 for cities of more than 100,000 people with full flushing | Metro cities |
| 200 | The upper end of the same range | The most generous allowance |
What does it assume, and what does it leave out?
- The figures are the design allowances for everything a person uses at home in a day, and the real use of your household may be lower or higher.
- It gives one day of demand as a single tank. How the water is split between an underground sump and an overhead tank, how much spare to keep for days when supply fails, and the height and position of the tank are design decisions. Ask your engineer or plumber.
- It is for a single house of up to 20 people. It does not cover flats, hostels, gardens, swimming pools or fire storage.
- The standard tank sizes are common sizes sold in India, not a requirement of any code.
Sources
- IS 1172:1993, Code of Basic Requirements for Water Supply, Drainage and Sanitation (clause 4.1, water per person per day).
- CPHEEO, Manual on Water Supply and Treatment (urban per-person norms).
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General information only. It is not a structural design or professional advice. Ask a licensed structural engineer or architect to check your plans and site.