138 LEAKAGE FROM STREET MAINS 



there is a possibility of leakage through the gates in the mains 

 and that such leakage will tend to reduce the apparent leakage 

 in the system. It is therefore necessary that every attention 

 should be given to the gates to make sure that they are properly 

 seated and to ascertain as far as possible that they are tight. 

 Also, that the remaining leakage is made up in part of leakage 

 from the main pipe and in part from defective or abandoned 

 services, and there is no certainty of finding out which is which. 



Examinations of this kind carefully carried out night after 

 night by competent observers will locate those blocks in a system 

 in which the greatest leakage from street mains occur, and if this 

 is followed up by further examinations of the pipes in the day time 

 for evidences of leakage and by digging out and recaulking those 

 pipes in which leakage is greatest, the loss can be reduced. 

 In any system where the pipe has been carefully and conscien- 

 tiously laid, it is to be normally expected that the pipe in a great 

 majority of blocks will be comparatively tight After some of the 

 worst sections have been located and corrected it will not pay to 

 go further. 



As to the Total Amount of Water Lost from Pipes in the 

 Streets. The most convenient basis for comparison with the 

 rest of the discussion is the average amount of water lost per 

 service. Most of the data are in terms of pipe sizes and lengths, 

 and a basis of comparison must be first found. 



For the purpose of this discussion 95 services per mile may 

 be taken. This is the figure reached in Chapter VIII, p. 96. 



The average size of pipe in the streets in a water works 

 system ordinarily ranges from about 6 inches for the smallest 

 systems to about 8 inches in larger systems. For the largest 

 cities the size exceeds 8 inches, and there is an upward tendency 

 in the average. 



For sixteen representative systems of companies for which 

 complete information is available the average size is about 7 

 inches. 



For the purpose of this discussion 8 inches may be taken as 

 the normal average size of pipes in the streets. The normal 

 leakage is to be taken as the leakage to be reasonably expected 



