152 SEWER DESIGN 



amounts seem large in view of the experimental data, but it 

 must be remembered that the amounts given in the experi- 

 mental data are for leakages through perfect joints, and that 

 in construction any workmanship except the best, which it is 

 practically impossible to secure in trench-work, will materially 

 modify and increase the amounts given. 



PROBLEMS 



47. The annular space for the joint in a lo-inch pipe (3-foot lengths) 

 is i inch. If the thickness of the pipe is inch and the leakage is at the 

 rate of 15,000 gallons per mile per day, determine the rate of infiltration 

 through the cement in gallons per square yard of area. 



48. The annular space of a 6-inch pipe is f inch and for a 1 2-inch pipe 

 \ inch. If the thickness of the pipes are f inch and i inch respectively, 

 compute the relative permeability, assuming the latter to depend on the 

 area of the joint. 



49. If the leakage through the walls of a brick sewer, 4 feet 6 inches 

 diameter, is at the rate of 5 gallons per square yard of interior surface, 

 compute the leakage per mile of sewer. 



50. If the leakage into a sewer system is at the rate of 25,000 gallons 

 per mile per day under a certain head, what would be the probable leakage 

 if the head is doubled, judging by Senior's experiments. 



51. Assuming the leakage into 6-inch pipe to be at the rate of 8000 

 gallons per mile per day, determine the total leakage into 10 miles of 

 6-inch pipe, 5 miles of 8-inch pipe, 2 miles of lo-inch pipe, and 0.75 mile 

 of i2-inch pipe. 



