462 APPLIED SCIENCE 



548. City Waterworks. A large community cannot use 

 wells to advantage because of the danger of contamination. 

 Therefore, it is necessary to secure water from a distance and 

 allow it to flow to the community. It is therefore pumped to 

 a basin, called a reservoir, which is situated at the highest 

 elevation in the vicinity. At the reservoir there is usually 

 erected a large steel stand-pipe to supply the water to the 

 houses near or on the same level as the reservoir. 



Water is pumped to a reservoir to secure a uniform pres- 

 sure which will force the water to the tops of buildings. As 

 water seeks its own level, it will rise in the buildings to the 

 height of the reservoir. This is called the gravity system 

 of waterworks, as the force that drives the water is the force 

 of gravity. While this system may be used to advantage 

 in some cities, in other cities an elaborate pumping system 

 must be employed. 



Water is conducted from the reservoir through broad pipes 

 called mains. Smaller pipes are attached to the mains and 

 run at an angle to the sidewalk. At the edge of the side- 

 walk there are valves, called hydrants, for shutting off or 

 turning on the water. The pipes enter the houses through 

 the cellars and pass through meters where the volume of 

 water is measured in gallons. Pipes are conducted from the 

 cellars to different rooms. Water is obtained from the pipes 

 by means of valves called faucets. 



649. Faucet. The faucet consists of a bar handle which 

 operates a screw. The screw raises or closes a disk to which 

 a leather washer is attached. If it closes the disk, the water 

 is prevented from running through to the opening. If the 

 disk is opened by turning the handle in the opposite direc- 

 tion, the water flows through the opening. If the washer 



