230 



GENERAL SCIENCE 



the pumps force it to the reservoirs and gravity delivers 

 it to the houses. New York City uses gravity to deliver 

 the water from the Catskills, but after reaching the city 

 the water has to be pumped in order to have sufficient 

 pressure. 



157. Why Water Pressure is not Uniform. Before 

 city reservoirs and standpipes are constructed, it is 



RESERVOIR AND STANDPIPE 



Standpipes used with the reservoir to keep a constant pressure at a 

 distance from the reservoir. 



necessary to ascertain the quantity of water needed in 

 order to determine how strong to make the walls of the 

 reservoirs and standpipes. The greater the height at 

 which the water stands, the thicker the walls must be. 

 The greater the elevation of the houses 

 that use the water, the stronger must 

 . be the pumps and the stronger must be 

 the walls of the standpipe to resist the 

 pressure. 



In order to understand how much 

 pressure water in a reservoir or stand- 

 pipe has, it is necessary to know the 

 weight of a cubic foot of water and the 

 Cubic foot of water pressure produced by water which is a 

 foot deep. A cubic foot of water 



i root 

 CUBIC FOOT 



weighs 62.5 pounds. 



at o C. weighs about 62.5 pounds; that is, when water 

 is one foot deep it presses down 62.5 pounds on every 

 square foot, or .434 of a pound on each square inch; or 



