AMOUNT OF SEWAGE PER CAPITA 139 



does not include, it is to be noted, any ground-water flow nor 

 any large manufacturing enterprises which may affect the 

 daily variation. 



Analyses, more in detail, have been made of the variation in 

 the flow, considering not only the daily maximum, but also 

 seasonal variations, taking the monthly maximum and adding 

 it to the weekly maximum, to the daily maximum, and to 

 .the hourly maximum. This method was given by Fanning in 

 his " Water-supply," and was quoted by Staley and Pierson. 

 Baumeister says that the days of greatest consumption require 

 one and a half times as much water, and hence the sewers 

 must be designed to carry off one and a half times the normal 

 flow. The hourly maximum is one and a half times the hourly 

 mean. Hence the capacity of the sewer must be such as to 



remove hourly - - of the average daily quantity, or 



more than twice the amount calculated on the supposition 

 that the same quantity was supplied each hour of the year. 

 In one of the recent German books on water-works by Franzius 

 and Sonne the daily maximum is fixed "at ij and the hourly 

 at if, making the average between the latter and the daily 



T V T 



average -^ = approximately.* 



24 1 2 



A common method of defining the maximum flow is to say 

 that one-half of the daily flow will run off in 6 to 8 hours, 

 and the sewer must be designed for this rate of flow. From 

 the diagrams given, and taking the midday hours when the 

 flow is greatest, the number of hours required to carry off 

 one-half of the daily flow is as follows: 



Binghamton, August 9 ................... io| 



10 



it it 



11 ................... 9* 



12 10 



" J3 icj 



Baumeister. 



