FARM WATER SUPPLY AND SEWAGE DISPOSAL 355 



The septic tank is a means of disposal of sewage from the 

 farm home. The septic tank alone will not purify sewage ; it 

 will partially purify it and put it in condition to be completely 

 purified by means of a filter or thru a system of tile. The 

 septic tank illustrated in Fig. 343 is a one-chambered tank. 

 Its action is as follows: In the septic tank the sewage 

 is acted on by bacteria minute organisms that thrive under 

 conditions where there is neither air nor light. The solids in 

 the sewage are broken down and put into solution. It must 

 be remembered that only one or less than one per cent 

 of the sewage is solids the rest is all water. Soon a thick 

 leathery scum forms on the surface of the tank; this indicates 

 that it is working properly. The solid part that is not dis- 

 solved settles to the bottom of the tank. It is necessary to 

 clean this out every few years. 



To completely purify this sewage, it is discharged onto a 

 filter or into a system of tile arranged to allow it to filter away 

 into the soil. In the filter or in the surface soil, there are bil- 

 lions of bacteria that thrive in the presence of air and light. 

 These are called the nitrifying bacteria. They completely 

 purify the sewage. This is nature's method of purification. 



325. The Art of Plumbing. Plumbing has been called 

 a sanitary art and defined as the art of placing in buildings, 

 pipes and other apparatus used for introducing water supply 

 and for removing wastes. 



The Plumber as a Specialist: In big jobs in large building 

 work, there are special plumbers for doing the heavy rough- 

 ing-in work, putting in the large pipes and the general net- 

 work of smaller pipes. Then there are other plumbers to do 

 the finishing work. 



