CHAPTER IV 

 GRAPHICAL COMPARISON OF METER RATES 



When the flat rate system fails, as it usually does in the long run, it is 

 usually succeeded by the meter system of charging. Halford Erickson, 

 Proc. Am. W.W. Assn., 1913, p. 53. 



The diversity of meter rates is such that a direct comparison 

 between schedules of rates in force in any two works cannot 

 ordinarily be made. To make a comparison it is necessary to 

 compute the annual bills for a number of assumed quantities 

 of water under each of the schedules and then to compare these 

 amounts with each other. Even then the comparisons may 

 differ at each of the points selected. To make the comparison 

 of value it is necessary to use a considerable number of such 

 points. At some points one schedule may be higher, and at 

 another point it may be lower, and in any case the ratios will be 

 variable. The business is too complicated to be compared ade- 

 quately in that way. 



To aid in understanding such figures, the results may be plot- 

 ted; that is to say, the annual bills for each annual quantity of 

 water may be made into a diagram. More conveniently, the 

 annual bills may be divided by the annual quantities and the 

 average annual payments per 1000 gallons for each quantity 

 ascertained and plotted. 



If such a series of results are plotted on a natural scale, 

 owing to the extremely wide range in quantities from the smallest 

 consumers to the largest, the results for the relatively small 

 takers must be shown upon too small a scale to be of practical * 

 use. If the scale is enlarged to show the bills of the smaller 

 takers properly, the diagram becomes so large that it is impracti- 

 cable to show the rates charged to the largest consumers. A series 



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