Dear Anita,
 
For designing a storage tank one of the important factor is the average daily
usage of water per capita, which is different for different areas depending upon
the

1.availability of water

2.Climatic parameters like temprature, rainfall etc 

3. Life style of the population etc. For example deserts people water need is
less as compared to the barrage area people because desert people has less
accessibility to water.
 
First you should know the per day per capita demand for water, then estimate the
population for whole building, then decide for how much time/years you are going
to design the storage tank, then decide for how many days you want to store the
water, consider the population growth rate and find the future population
need/demand by the formula  Pp(1 + n/100)^N  (This formula will give you the
future population)
inwhich Pp = Current Population
n = Population growth rate
N= Numbers of  years for which you want to design
 
I hope above hints will help you. If you need further help, then donot hesitate
to contact me.
 
Kind regards,
Habib

Engr. Habib ur Rehman
Irrigation and Water Management Advisor
Catholic Relief Servics
House # 8, Street # 60, F-7/4
Islamabad, Pakistan
Cell # 0092 300 9110122


--- On Fri, 7/18/08, anita bhatt <anitajnu2001@...> wrote:

From: anita bhatt <anitajnu2001@...>
Subject: [hydrologymodel] Overhead Tank Capacity: Calculation:Ranchi
To: hydrologymodel@...
Date: Friday, July 18, 2008, 11:49 AM

Dear Sir/Madam,

I am staying at Ranchi, the capital of Jharkhand, in a building comprising of 34
flats. I would like to know the minimum storage capacity of overhead water
tanks. Please give the details of calculation.

Note: - There is no underground water tank. The overhead tanks are to be fed
through deep well boring and used to service all the needs of the residents.

regards,
Anita Bhatt