How Many Litres of Water Per Person Per Day?

The sizing norm comes from IS 1172:1993 (Code of Basic Requirements for Water Supply, Drainage and Sanitation): it recommends 150–200 litres per head per day for residences with full flushing systems, with 135 lpcd retained as the minimum for LIG/EWS housing — and 135 lpcd is the figure CPHEEO and most municipal planners use as the standard urban norm. Of that, roughly 45 L is flushing and the rest covers drinking, cooking, bathing and washing.

What the breakdown looks like in practice at 135 lpcd: roughly 45 L for toilet flushing, 20 L bathing, 40 L washing clothes and utensils, and the balance for drinking, cooking and cleaning. Actual metered consumption varies enormously — surveys find urban Indian households ranging from under 70 lpcd where supply is constrained to well over 200 lpcd in unmetered high-supply homes.

For tank sizing the norm matters more than your exact usage: multiply persons × 135 (or 150–200 for a full-flush home) × the days of storage you want, then round up to a standard size with the household calculator.