60 



Our Surroundings 



remaining organic matter harmless. When the tank has only two 

 sections the liquid is discharged into the soil from the second 

 section. This method of sewage disposal requires a water reser- 

 voir in the attic or some elevated place into which water has 

 been forced from a cistern or other source of supply by some 

 kind of pumping apparatus. 



Method in Urban Districts. In large towns and cities, the 

 sewage leaves the houses in pipes leading into larger underground 

 pipes which conduct it to a still larger pipe from which it is finally 

 discharged into some body of water, or into immense septic tanks 

 similar in structure to the small septic tanks just described. In 

 cities on the shores of the ocean or of large lakes, the largest pipe 

 is sometimes extended quite a distance into the water, where the 

 sewage is discharged and widely scattered by the tides and the 

 currents. 



Cities on the banks of rivers often discharge their sewage into 

 the river water. Although this method may be inexpensive, it is 

 clearly unfair to other cities farther down the stream which take 

 their drinking water from that source. Wherever sewage is dis- 

 charged into the water supply of a community, 

 a disposal plant should be maintained. Not to 

 do this is a menace to the health of that com- 

 munity. 



House Plumbing. Plumbing is the ar- 

 rangement of pipes and other apparatus to 

 carry water into, through, and out of a build- 

 ing. It is especially necessary as an aid in 

 the disposal of sewage. 



Drains are of the greatest importance 

 from a sanitary point of view. They should 

 be so constructed that no gases given off by 

 waste matter can escape into the house; 

 therefore they should be made entirely of metal and should 

 be air-tight. Iron is commonly used for making the larger and 

 longer pipes, and lead for the smaller and shorter ones. The 

 main drain pipe should be ventilated and every opening should 

 be protected by a trap. A trap consists of a bend, like the 



A WATER TRAP 



This keeps out sewer 

 gas. 



