In this article, we explained different types of water demand like domestic water demand, commercial water demand, public water demand, fire demand, and other water losses. Also explained how to calculate water requirement of fire demand in the city.
So please read the article till the end.
Types of Water Demand:
It is necessary to determine the consumption and fluctuation of water demand, on a daily, weekly, monthly, and yearly basis, before designing any type of water supply scheme.
But first of all we need to know how water will be used.
It is not entirely possible to determine the actual consumption of water, but according to certain empirical formulas and different types of water consumption based on experience can be shown as follows:
- Domestic water demand
- Commercial and Industrial water demand
- Fire control water demand for Fire fighting
- Public water demand
- Other Losses or Wastage of water
1. Domestic water demand:
Domestic use of water i.e. for drinking, bathing, washing clothes, cleaning of house and toilets, etc. as well as water consumption for cooking.
Generally household consumption of water depends on the following factors:
- Personal habits of people
- Social status of individual
- Local climatic condition
- Customs of the local people
According to I.S.-1172-1971, 135 liters/day per person is required for water in our country. While in developed countries this ratio is around 350 lit/day/capita.
|Sr. No||Water uses||Water consumption in liters/day/person|
|3.||Flushing of W.C||30|
The reason behind this difference is the comparatively high consumption of water in the modern facilities of developed nations such as air-conditions equipment, air-coolers as well as other equipment.
Generally about half (50%) of the total daily amount of water is spent on household consumption.
Also Read: WATER TREATMENT PLANT DESIGN PPT
2. Commercial and Industrial water demand :
Commercial or industrial places include private as well as public recreation areas, hotels, offices, shopping centers as well as manufacturing facilities such as factories and warehouses.
In this type of water demand, the water supply scheme should be designed keeping in view the consumption of about a 1/4 to 1/3 part of the total water consumption.
Such consumption depends on the structure of the city and its business development as well as the development of the population and the area.
Water requirement for building other than residential
|Sr. No||Type of Building||Water consumption per capita par day liters|
|1.||Factories with bathrooms||45|
|2.||Factories without bathrooms||30|
|3.||Hospital including laundries.|
(a) No of beds not exceeding 100
(b) No of beds exceeding 100
|4.||Nurse homes and medical quarters||135|
|7.||Hotel (per bed)||180|
|8.||Restaurant (per seat)||70|
|9.||Cinema halls and theaters||15|
(a) Day school
(b) Boarding School
3. Fire control water demand for Fire fighting
Fires usually occur in densely populated areas or in industrial estates or factories. Fires cause severe damage to people’s property and sometimes even loss of life.
There are many causes of fire such as electrical short circuit, the explosion of ammunition, fire inflammable substances or chemicals, intentional fire by criminal elements, and also accidental fire as a result of an accidental mistake.
Fire brigades or fire fighting squads are deployed in every city or municipality for fire fighting. Therefore, special water mains, as well as fire hydrants, are installed on the main water lines to control the fire from where the required water is obtained.
Generally 5 to 10 percent of the main water supply is reserved for fire fighting purposes.
This quantity for fire fighting is calculated using the following empirical formulas:0.
|Sr. No||Type of Urban area||Required amount of water per lit/min|
|1.||The area with low height||2200 lit/min|
|2.||An urban area with tall buildings||4500 lit/min|
|3.||Market area or area with the valuable colony||7500 to 13500 lit/min|
|4.||Three storied and densely populated colonies.||approx 27000 lit/min|
a. National Board of Fire underwriter’s formula:
Q = 4637 √P (1-0.01 √P)
Q = the amount of water required in liter/minute
P = the population of the city in the number of thousands
b. Kuichling’s Formula:
Q = 3182 √P
c. Freeman’s formula:
Q = 1136 ( (P/5) +10)
F = 2.8 √P
F = number of required streams
d. Boston’s formula:
Q = 5663 √P
All the above formulas are adopted for every type of area except the type of houses, location as well as type of area, etc.
Kuchling’s formula corresponds to the position of our country and gives satisfactory results.
Fire fighting water supply is generally considered as required for residential urban areas as per the following standards:
4. Public water demand:
Public water demand includes water consumption in public places such as hospitals, schools, colleges, town halls, religious places, prisons, inns, etc. also includes water required for public fountains, road cleaning, cleaning of the sewer system, etc.
Generally 7 to 10% of the water supply is allocated for public water consumption.
Water Requirement for public purpose
|Sr. No||Purpose||Water Requirement|
|1.||For Public parks||1.4 lit/m2/day|
|2.||Street washing||1 to 1.5 lit/m2/day|
|3.||Sewer Cleaning||4.5 lit/m2/day|
Water Requirements for Live stock
|Sr. No||Live stock||Water requirements lit/animal/day|
|1.||Cows/Buffellow||50 to 65|
|2.||Hogs||18 to 20|
|3.||Chickens and hens||1.2 to 1.5|
|4.||Goats||12 to 15|
|5.||Horses||40 to 50|
|6.||Sheep||12 to 15|
5. Other Losses or Wastage of water:
The full amount of water distributed from the water supply scheme does not reach the consumers. The main reasons for this are as follows:
- Defective pipe joints
- Cracks in pipelines
- Breakage in pipelines
- Faulty valves and fittings
- Loss due to carelessness consumers
- Water theft due to unauthentic connections
Generally 15% of the water supply is allocated for Other Losses or Wastage of water.
Example of calculating Fire control water demand:
To build a fire fighting system for a city with a population of 150,000. Rate the amount of water required for this using different formulas.
P = Population = 1,50,000 people (150 thousand)
Q = Quantity of water =?
Now, using the common formulas used for fire fighting:
(a) Using the National Board of Fire Underwriter formula
Q = 4637 √P (1-0.01 √P)
= 4637/150 ((1 -0.01) √150)
= 4637 x (12.247) x (1 – 0.12247)
= 49834 liters/minute
(b) Kuchling’s formula:
Q = 3182 √P
= 38970 liters/minute
(c) Using Freeman’s formula:
Q = 1136 ( (P/5) +10)
= 1136 ((150/5) + 10)
= 45440 liters/minute
(d) Boston’s formula:
Q = 5663 √P
= 5663 √150
= 5663 x 12.247
= 69355 liters/minute
Note: According to Kuchling’s formula for Indian urban area, the city should be supplied with water at the rate of about 38970 liters/minute.