SEWER DIAGRAMS 189 



instead of the numbers themselves. The advantage of this 

 method of plotting, shown in the good intersections, is evident. 

 The diagram shown in Fig. 47 is given as being convenient 

 for laying out laterals. By its use the greatest length possible 

 for a 6-inch pipe flowing full to be laid for contributing house- 

 drains can be read off at once. As the diagram shows, the 

 first factors are the width of lots and the probable number 

 of persons per lot. This is changed into the number of per- 

 sons for one hundred feet of sewer and combined with an 

 assumed number of gallons per head per day. This gives gal- 

 lons per hundred feet of sewer, which, taken with the grade 

 of the sewer, gives gallons capacity of length of sewer, to which 

 the assumed contribution is made. A similar diagram can 

 easily be made for 8-inch pipe. 



PROBLEMS 



72. Using values found in Flynn's Tables, construct a diagram on 

 cross-section paper, having slopes in feet per thousand for abscissae and 

 discharge in million gallons per day for ordinates. 



73. Construct three curves, showing the relations between sizes of 

 pipes and slopes in per cent by which velocities of 2.0, 2.5 and 3.0 feet per 

 second may be obtained according to Kutter's formula. 



74. Construct a diagram on logarithmic paper for circular pipes 

 flowing half-full, with slopes in feet per thousand for abscissae and dis- 

 charge in cubic feet per second for ordinates. Show curves for both 

 sizes of pipes and for velocities. 



75. Using the Williams-Hazen formula, construct a diagram to show 

 relation between slopes and discharges for pipes 6 to 24 inches diameter 

 on logarithmic paper. 



76. Construct a diagram for elliptical pipe (or for a basket-handle 

 section) showing discharges for various sizes and slopes. 



77. Construct a diagram for conduits whose section is a right tri- 

 angle, vertex down, showing discharges for various depths and slopes. 



