HYDRANTS AND TRAPS 209 



235. Plumbing. In some cities water is sold to con- 

 sumers at a "flat rate," without regard to the amount 

 used. Other cities use a meter, or measuring device, 

 which records the amount that actually flows from the 

 street mains into the house. The pipes, faucets, traps, 

 etc., through which water is carried to the different parts 

 of the house, or away from it, make up the plumbing of 

 the house. The word "plumbing" is from plumbum, 

 Latin for "lead." To make lead pipes, men force hot 

 lead, under great pressure, through steel dies having 

 ring-shaped openings. Nowadays iron pipes, as well 

 as lead ones, are used for plumbing. The iron is "gal- 

 vanized" to prevent rusting (cf. 222, Ex. 4). 



Lead is used for pipes, sink linings, etc., because it is 

 not rusted readily (cf. 216). Lead pipes are also easy 

 to bend around corners and into special shapes. Then, 

 too, they can be cut readily where necessary, and the 

 pieces joined by solder. 



But the use of lead has one disadvantage, in that the fresh surface 

 of the metal is acted upon, and dissolved, by water. When lead is 

 taken regularly into the body, as in drinking water, it accumulates until 

 it causes sickness. Painters often have " painters' colic" because of 

 the lead compounds in paint (cf. 229) . Lead is not acted upon greatly 

 by pure water; but air and soft water, especially if carbon dioxide is 

 present (cf. 80, table), gradually " dissolve" it. Hard water acts 

 upon the inside of the pipe after a time, and produces a coating that 

 does not dissolve. This protects the lead and the water. We should 

 always let water run for a moment from a new lead pipe, so as to make 

 sure that the water we drink is free from lead compounds. 



236. Hydrants and Traps. Faucets, or hydrants, are usually of 

 brass, sometimes plated with nickel. They are generally of two kinds: 



(1) Those having a movable, tapered plug with a hole in it. 



