THE COST OF WATER 



213 



source of the supply is more or less on a level with the sur- 

 rounding land, the cost is great, because the supply for 

 the entire city must either be pumped into an artificial reser- 

 voir, from which it can be distributed, or else must be driven 

 directly through the mains (Fig. 154). 



A gallon of water weighs approximately 8.3 pounds, and 

 hence the work done by a pump in raising a gallon of water 

 to the top of an average house, an elevation of 50 feet, is 

 8-3 X 50, or 415 foot pounds. A small manufacturing town 

 uses at least 1,000,000 gallons daily, and the work done by a 



FIG. 154. Water must be got to the houses by means of pumps. 



pump in raising that amount to an elevation of 50 feet would 

 be 8.3 x 1,000,000 x 50, or 415,000,000 foot pounds. 



The total work done during the day by the pump, or the 

 engine driving the pump, is 415,000,000 foot pounds, and 

 hence the work done during one hour would be ^ of 

 415,000,000, or 17,291,666 foot pounds ; the work done in one 

 minute would be g 1 ^ of 17,291,666, or 288,194 foot pounds, 

 and the work done each second would be g 1 ^ of 288,194, or 

 4803 foot pounds. 



A i-H.P. engine does 550 foot pounds of work each 

 second, and therefore if the pump is to be operated by 

 an engine, the strength of the latter would have to be 8.7 

 H.P. An 8.7-H.P. pumping engine working at full speed 

 every second of the day and night would be able to supply 



