160 SMALL WATER SUPPLIES. 



the water impinging against them, thus emitting a 

 sound similar to the air impinging against the reed 

 of an organ pipe. 



To avoid this a hard material should be used for 

 washers, such as vulcanized rubber. Ball-valves too 

 light for the purpose may cause noise and should 

 not be used. Heavy fittings of this kind are always 

 best, having all burrs and sharp edges removed 

 from the inside. In fact, attention should always be 

 paid to the brass fittings of water supply schemes, 

 and the best quality used. This is a matter which 

 may escape attention in country work, town supplies 

 being under regulation by the local authority as to 

 class of fittings used. 



The lead service pipes used should also be heavier 

 than actually required. To calculate the strength 

 of lead pipes the thickness and tearing strength must 

 be known. This latter is 2160 Ib. per sq. in. Conse- 

 quently, if we know 



t = thickness of pipe in inches, 



2160 

 5 = = 360, 



r = radius of pipe, 



p = water press. Ib. per sq. in., 



. t x 5 



then/ = - v 



In the case of i in. lead pipe, 



('2 X ^6o\ 

 -*- -- J = i44lb. persq. in. ultimate, 



or a safe pressure of 



- = 48 Ib. per sq. in. 



