# Overhead tank capacity calculation in Ranchi, Jharkhand

22

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.

Sanjay Verma, Ranchi.
akshits64@yahoo.co.in

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22 Responses

Dear Sanjay Verma,

To assess the capacity of water tank, certain assumptions are to be made.
1. Assuming 4 dwellers residing in 1 flat.

2. Assuming each will consume about 200 litres of water per day in peak season i.e. in summer.

Quantity of storage per day = 34 flats X 4 X 200= 27200 i.e. approx. 28000 lit per day.

At least 4 tanks will be required to cater the demand then.

Capacity required for each tank= 28000/4 = 7000 litres.
Concrete tank will be more useful to decide the sizes= 7 cum capacity.
Sizes approx. for each tank = 2.5 X2.2X.1.3 (depth).

Regards,

Lalit Bokolia
Joint Director
National River Conservation Directorate
Ministry of Environment and Forests
Government of India

Dear Sanjay Verma,

The overhead tank should supply about 34 X 1500 litres (assuming 5 persons in a house) i.e, 51,000 litres of water per day for comfortable use of water for all purposes for the whole complex. If it is filled twice a day, the tank capacity can be 26,000 litres or 26 cubic meters.

S.V.Vijaya Kumar
vkumarsv@yahoo.com

Dear Sanjay Verma,

Calculations for designed capacity of Tank & Pump

Total no. of flats = 34
Av.population = 5 persons/flat (taken)
Total population = 34X5 =170

For Ranchi

Av. Domestic water consumption for Indian town with full flushing system = 200 lt/head/day
(As per IS: 1172-1993)
Av. Daily Demand (ADD) of Water = Av. water consumption X population = 200 X 170 = 34000 lt/day
Max. Daily Demand (MDD) of Water @180% of ADD = 180/100 X 34000 = 61200 lt/day

Designed capacity of Tank (minimum) = MDD of Water = 61200 lt.
Designed capacity of Pump = 2 times of ADD = 34000 X 2 = 68000 lt/day
Designed capacity of Pump = 24/8 X 68000 = 204000 lt/day (say, operated for 8 hrs/day)

Thank you

S. Halder
Assistant Engineer (Agri- Irri)
Water Investigation & Development Department
Government of West Bengal

Are you sure of what you're saying, always saying design capacity? Where's the design now? Dimensions? Thickness? Height of the tank from the slab? The plan view? Where?

Dear Sanjay Verma,

As per the Urban Ministry's calculation 135 litres is the requirement /person/day. Please calculate for the no. of persons staying in the Apt. bldg. in 34 flats. For an approximation 4 persons are estimated to live in a flat. So 34x4x134 litres is to be kept in the overhead tank. Since the Apt bldg has a pumping system you do not need a Reserve except when your pumps

Regards,

Dr.V.N.Sharma
vnsh44@gmail.com

Sir,

I find your input very useful. The approach is very logical and I think 140 liters per head per day is a more reasonable estimate, even considering some amount of losses.

Dear Sanjay Verma,

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 temperature, 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 have 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) in which 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 do not hesitate to contact me.

Kind regards,

Engr. Habib ur Rehman
Catholic Relief Services

Dear Sanjay Verma,

The capacity of overhead tank shall be calculated on the basis of residents. 34 flats x 5 residents per flat x 200 liters/capita water = 34000 liters. You may consider a tank of size 4m x 4m x 2m + 0.3m free board. This way, the roof slab shall be designed for a load of 2.5 tons/sqm.

With best regards,

Taral Kumar
Executive Director
Akar Impex Pvt. Ltd.
E-9, Sector 6, Noida

Dear Sir,

This is with respect to your comment in July 2008 to Sanjay. I want to know some of the following aspects of size of overhead tanks.

In an urban location, if we want to go for more storage of water or use a bigger O.H. tank: How we should calculate the load on the roof due to O.H. tank? What is the limit on the load bearing capacity of the roof? How to arrive at the limiting value of the tank size to be placed on building roof?