WATER SUPPLY, PLUMBING, ETC., FOE COUNTRY HOMES. 
33 
the soil pipe, and connections should be tightly made. The sewer 
inside the cellar wall should always be soil pipe; tile should never be 
used except outside of the wall. A soil-pipe trap should be provided 
at the house foundation, as shown in figure 26. Every fixture should 
have a trap to prevent foul air from coming back through the waste 
pipe. Vent pipes should be provided on all waste pipes to prevent 
siphonage and the consequent destroying of the traps. Figure 27 
(p. 34) shows a good arrangement of sewer plumbing. 1 Note the 
traps and vent pipes on each waste pipe. The least sizes of waste 
and vent pipes are given in the table below. 
Sizes of icaste and vent pipes. 
Name of pipe. 
Diameter. 
Name of pipe. 
Diameter. 
Inches. 
4 
'! 
l|-2 
11-1* 
ii 
3^-4 
Wash tubs, lA-inch waste pipe to 2- 
Inches. 
U- 2 
JBranctt waste pipes for kitchen sinks. . 
9 
2 
Basin waste pipe. 
Branch vents for traps over 2 inches.. . . 
Branch vents for traps less than 2 inches 
2 
All plumbing should be tested by filling with" water or smoke to 
detect leaks. 
SEWAGE PURIFICATION AND DISPOSAL. 
The problem of the purification and disposal of farm sewage by 
small private systems differs somewhat from that of city sewage dis- 
posal, owing principally i:o the extreme fluctuations in flow, small 
size of the system, fresh character, and variation hi the quality of 
the sewage. 
The process of sewage disposal is partly mechanical and partly 
bacterial, consisting of (1) preliminary or tank treatment and of (2) 
final treatment, which is application to a natural soil by surface or 
subsurface distribution or to a specially prepared filter. 
PRELIMINARY OR SEPTIC-TANK TREATMENT. 
The exact nature of the action which takes place hi a septic tank is 
a subject of dispute among sanitary experts and bacteriologies. 
Several theories have been advanced, but it is apparent that no 
definite conclusion has been reached. Some authorities advocate 
the use of open ventilated tanks, others advocate the use of air-tight 
tanks. 
Experience has shown that, in a small sewage disposal system, a 
dark, air-tight tank of sufficient capacity and so constructed that 
sewage may remain in it entirely at rest for a period of from IS to 24 
I niv. Mo. Engin. Expt. Sta. Bui. 3. 
