CITY WATER SUPPLY 



231 



the pressure is .434 of a pound per square inch for each 

 foot in depth. If the water is 10 feet deep the pressure 

 is .434 X 10, or 4.34 pounds per square inch; if it is 30 

 feet deep the pressure is 13.02 

 pounds per square inch on the bot- 

 tom of the vessel or reservoir. 

 Standpipes 100 feet high full of 

 water have a pressure of 43.4 

 pounds per square inch at the 

 bottom. 



The pressure against the side of 

 the standpipe near the bottom is 

 almost the same as the pressure on 

 the bottom. The pressure against 

 the side of the standpipe halfway 

 up is half the pressure at the bot- 

 tom. If the standpipe were tapped at the bottom and 

 also halfway up from the bottom, the water would flow 

 out with a force twice as great at the bottom as it 

 would at the upper spout. If the standpipe is only half 



HEIGHT OF WATER DE- 

 TERMINES THE PRESSURE 



PUMPING SYSTEM 

 Used in level countries, assisted by standpipes. 



full, the water pressure at the bottom is only one-half as 

 great as when it is full to the top. From this we see that 

 if the height of the water in the standpipe varies, the 

 pressure in the pipes leading from it to the houses will 



