SANITARY PLUMBING 



505 



of gases. Many of these gases have offensive odors and they 

 are genreally regarded as being very unhealthful. Some of 

 these gases while nearly without odor are just as unhealthful. 

 The drains must be so constructed as to prevent the escape 

 of these gases into the building. 



To insure air-tight construction all drains within the build- 



' t* ' . } ^^- '' '' i*--'-'^- ' --..">, ~ - -I, '< .;.',-" ', 



~TFIAP TRAP 



FIG. 313. Plumbing in a residence. 



ing must be of metal. The larger and straighter pipes are 

 generally of iron with all joints closed by means of calking 

 with oakum and lead; the smaller and bent pipes are often of 

 lead with all joints wiped, i.e., soldered. 



593. Venting the Drains. The main drain pipe should be 

 thoroughly ventilated, i.e., provision should be made whereby 

 a current of fresh air passes constantly through the drain pipe 



