Water Demand

The community, society and industry need water for different uses. Water consumption in a community is characterized by several types of demand, including domestic, public, commercial and industrial uses. Domestic demand includes water for drinking, cooking, washing, laundering and other household functions. Public demand includes water for fire protection, street cleaning and use in schools and other public buildings. Commercial and industrial demands include water for stores, offices, hotels, laundries, restaurants and most manufacturing plants. There is usually a wide variation in total water demand among different communities. This variation depends on population, geographic location, climate, extent of local commercial and industrial activity and the cost of water.

An accurate estimation of water demand helps to determine the quantities of water when the water will be used various demand patterns. Water demand is the accurate estimation of total water. The unit of water demand is lpcd (liter per person (capita) per day). While planning the water supply scheme for an area, it is essential to determine the total water required for different purposes. 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. Different types of water demand include the following. 

1) Domestic Water Demand 

Domestic Water demand includes the water required for drinking, cooking, bathing, lawn sprinkling, gardening, sanitation purpose, etc. It depends upon habits, social status, and climatic conditions of people. Domestic water demand accounts for 55 to 60% of the total water consumption. As per IS 1172-1983, the domestic consumption in India accounts for 135 lpcd (liters/capita/day) without full flushing system. The value is 200 lpcd with full flushing system. Generally about half (50%) of the total daily amount of water is spent on household consumption. The 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

2) Industrial Water Demand 

The per capita consumption of industries is generally taken as 50 lpcd. It represents the need of industries, either existing or likely to start in the future. This quantity will thus vary with the number and types of industries present in the city. 

3) Institutional and Commercial Water Demand 

On an average, per capita demand of 20 lpcd is required to meet institutional and commercial water demand. For highly commercialized cities, this value can be 50 lpcd. It includes the use of institutions such as hospitals, hotels, restaurants, schools and colleges, railway stations, offices, etc. This quantity will certainly vary with the nature of the city and with the number and types of commercial establishments and institutions present in it.

4) Public and Civil Use 

The per capita consumption for public and civic use can be taken as 10 lpcd. This water is used for road washing, public parks, sanitation etc. This includes watering in a public park, gardening, washing, sprinkling on roads, use in a public fountain etc. 

5) Fire Demand 

The fire demand is generally taken as 1 lpcd. It is the amount of water required for firefighting purpose in case of a fire break out in an area. Per capita fire demand is ignored while calculating the total per capita water requirement of a particular city because most areas have fire hydrants placed in the water main at 100 to 150 meters apart.This water is required to be available at a pressure of about 100 to 150 kN/m^2or 10 to 15m head of water. If the population is less than 50000, fire demand is not calculated. For larger city fire demand was calculated. 

6) Waste and Thefts 

This consumption accounts for 55 lpcd. Even if the waterworks are managed with high proficiency, a loss of 15% of total water consumption is expected. This includes water loss in leakage due to bad plumbing or damaged meters, stolen water and other losses and wastes.

As Per IS 1172 : 1993 Indian Standard Code of Basic Requirements for Water Supply, Drainage and Sanitation

Water Supply for Residences (As Per IS 1172 : 1993)

A minimum of 10 to 100 liter per head per day may be considered adequate for domestic needs of urban communities, apart from non domestic needs as flushing requirements. As a general rule the following rates per capita per day may be considered minimum for domestic and non domestic needs. 

Rate of Demand for Various Communities (As Per IS 1172 : 1993)

Sl. No.	Type of Community	Rate of Demand (lpcd)
1	For communities with population up to 20000 and without flushing system	40 lpcd (min)
	a) water supply through stand post
	b) water supply through house service connection	70 to 100 Ipcd
2	For communities with population 20000 to 100,000 together with full flushing system	100 to 150 Ipcd
3	For communities with population above 100000 together with full flushing system	150 to 200 lpcd

It is also noted that the value of water supply given as 150 to 200 liter per head per day may be reduced to 135 liter per head per day for houses for Lower Income Groups (LIG) and Economically Weaker Section (EWS) of society, depending upon prevailing conditions. Out of the 150 to 200 liter per head per day, 45 liter per head per day may be taken for flushing requirements and the remaining quantity for other domestic purposes.

Minimum requirements for water supply for buildings other than residences shall be in accordance with the following table.

Water Requirements for Buildings Other than Residences (As Per IS 1172 : 1993)

Sl. No.	Type of Residence	Rate of Demand (per liter, day)
1	Factories where bathrooms are required to be provided	45 per head
2	Factories where no bath rooms are required to be provided	30 per head
3	Hospital ( including laundry) a) Number of beds not exceeding 100	340 per head
	b) Number of beds exceeding 100	450 per head
4	Nurses' homes and medical quarters	135 per head
5	Hostels	135 per head
6	Hotel	180 per head
7	Offices	45 per head
8	Restaurants	70 per seat
9	Cinemas, concert halls and theatres	15 per seat
10	Schools	45 per head
	a) Day schools
	b) Boarding schools	135 per head