water calculation---How much water does an urban citizen need?

In India, the design of water supply systems has been done using certain standards. Currently the standard being used is BIS 1172: 1993, reaffirmed in 1998. This specifies a consideration of use of the following:

For communities with a population of between 20,000 to 100,000 — 100 to 150 litres per head per day

For communities with a population of over 100,000 — 150 to 200 litres per head per day.

In its previous avatar there was also an attempt made in IS 1172 to understand the break-up of this demand which was then put as 135 litres per person per day. The break-up was as follows:

Bathing: 55 litres

Toilet flushing: 30 litres

Washing of clothes: 20 litres

Washing the house: 10 litres

Washing utensils: 10 litres

Cooking: 5 litres

Drinking: 5 litres.

Read more from source:: http://www.thehindu.com/features/homes-and-gardens/how-much-water-does-an-urban-citizen-need/article4393634.ece