Water tank size for a family of 4
Daily need ≈ 540 litres (4 × 135 lpcd, IS 1172 norm). Recommended standard tank: 1,000 L for 1.5+ days of storage.
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.
Fine-tune with the household calculator — change days of storage or the lpcd figure and it rounds to the next standard size for you.
FAQ
What size water tank for a family of 4?
Daily need is about 540 L at the IS 1172 norm. With 1.5 days' buffer for intermittent supply, a 1,000 L tank is the comfortable standard choice.
Should I size for 135 or 200 lpcd?
135 lpcd is the standard planning norm; full-flush urban homes per IS 1172 run 150–200 lpcd. If your usage is high (gardens, RO wastage), size with the calculator at 200.
One big tank or overhead + underground sump?
Most Indian homes pair an underground sump (bulk storage from intermittent mains) with a smaller overhead tank pumped from it — see overhead vs underground.