142 UNDER-REGISTRATION OF METERS 



It is entirely feasible, and has frequently been carried out in practice, 

 when required, to produce disc meters of the f and f-inch sizes that will 

 indicate from 50 to 75 per cent of the quantity discharged when the rate of 

 flow is as low as YO cubic foot per hour. 



This rate of flow is equal to only 18 gallons per twenty-four 

 hours. 



G. Bechmann, Engineer of the Paris Water Works, stated:* 



At Paris the regulations in force require that the registration must be 

 comparatively exact, that is to say, with a tolerance not exceeding 20 per 

 cent for even very small outputs not exceeding from T^Vrr to -g^o" of the 

 maximum ordinary capacity as well as the full registration of larger quan- 

 tities. These conditions rigorously and strictly enforced have limited some- 

 what the number of kinds of meters that could be used. 



It is common water works experience that old meters brought 

 into the shop after having been in service some years are less 

 sensitive and require larger flows to move them. 



In tests made by J. Waldo Smith,! seven f-inch meters 

 when new, purchased in the open market from well-known 

 makers, commenced to register with flows ranging from 19 to 

 390 gallons per twenty-four hours, with an average of 123 

 gallons as the minimum amount that would move the register. 

 After making various tests and after finally standing four months 

 connected up under pressure without being run, the amount of 

 flow that was required to start registration in the five of the 

 meters that were still serviceable averaged 440 gallons per 

 twenty-four hours and in no case was it under 300 gallons. 



Meters with Packing. In Europe, meters which measure 

 as a result of the movement of a piston provided with an ade- 

 quate and approximately water-tight packing, have been exten- 

 sively used, and the art of constructing such meters has reached 

 a considerable state of development. Such meters are much 

 more expensive than the disc and rotary meters that have 

 been commonly used in America. 



It may be that the use of some form of a packed meter will 

 ultimately prove advantageous in America. At any rate, the 



* " Distributions D'Eau," Paris, p. 440, 1888. 

 t Trans. Am. Soc. C.E., Vol. XLI, p. 359, 1899. 



