PLUMBING AND WATER SUPPLY 463 



becomes loose or wears away the water escapes until a new 

 washer is added. 



550. Water Hammer. Water under pressure in pipes 

 is subject to the force of gravity in the same manner as a 

 body falling through the air. -To illustrate: When water 

 flowing through a pipe is suddenly checked, a noise is heard, 

 caused by the striking of the water against the end of the 

 pipe or whatever stops the flow. The noise is heard at every 

 part of the pipe and in case of a long length of pipe the noise 

 appears to repeat itself very quickly. This " chattering" 

 is called water hammer. Water faucets that shut off 

 the water quickly always have water hammer. Its effect 

 is often sufficient to break a pipe. Faucets that gradually 

 check the flow of water overcome water hammer. An 

 air cushion at the end of pipe will often overcome this 

 noise. 



551. Water Meter. When the public realize that water 

 is measured, the consumption is less per capita (per per- 

 son) than when it is not measured. Therefore, within 

 the last few years drinking water has been metered in 

 many cities; that is, the water is run through a measur- 

 ing device that records in gallons the amount of water which 

 passes. 



552. Sewerage. The disposal of waste water and sewer- 

 age is a very important question. In the country, where 

 houses are not thickly settled, the waste water is allowed to 

 drain into the ground. The sewerage is disposed of by 

 using it as manure or by covering it with dirt to prevent the 

 odor from escaping. 



