Assessment of Variations:

After assessing the total water requirement for different uses of a water supply scheme, peak discharge has to be assessed so that the components of the scheme such as source of supply, pipe mains, pumps, filters and allied units, service reservoirs and distribution system might be of sufficient capacity to meet the requirements. The little the town, the more variable will be the demand. The maximum monthly, daily or hourly demands are expressed as ratio of their means. For an average Indian town, the maximum daily consumption is taken as 180% of the average. Hence, maximum daily demand = 1.8 × Annual average daily demand.

The maximum hourly consumption is taken as 150% of the average hourly consumption of the day correspondingly to maximum consumption:

∴  Max Hourly consumption or peak demand

= 1.5 × 1.8 × Annual average hourly demand

= 2.7 × Annual average hourly demand

However, Peak factor is normally taken on the basis of size of population of any town or city. Table gives the recommended Peak Factors.

Table: Peak Factors for Cities and Towns