858 



PARKS 



tion field offers the best means of disposing of the effluent from small septic 

 tanks. An absorption field consists of underground lines of field tile laid 

 with open joints, through which the effluent from the septic tank seeps into 

 the adjacent soil (Plates 335, 336 and 337). The liquid thus brought into 

 contact with the soil is absorbed and, under the proper circumstances, an 

 ultimate disposal is satisfactorily effected. 



A water-tight pipe of cast-iron or vitrified clay four or six inches in 

 diameter is laid from the septic tank or siphon chamber to the absorption 

 field. This pipe should have a fall of two per cent and terminate in a diver- 

 sion chamber (Plate 336). The tile lines of the absorption field are laid at 

 varying distances apart, usually four to fifteen feet, according to the nature 

 of the soil, and about one foot below the surface of the ground (Plate 337). 

 The tile lines should have a fall of about two inches in one hundred feet. 

 As a rule four-inch tile is used, the number of rows of tile and the length of 

 the tile lines depending upon the number of people to be served. The joints 

 of the tile drains are separated from one-fourth to one-half inch and the 

 tiles are laid in a bed of broken stone, gravel or other coarse material, 

 which will aid in absorption and prevent earth from entering at the joint. 

 Approximately fifty lineal feet of four-inch tile will be required for each 

 person contributing to the system, but this may vary from thirty to one 

 hundred feet depending upon the absorbing qualities of the soil. 



The proper amount of sewage is released into the tiles at regular inter- 

 vals by means of an automatic siphon or dosing chamber (Plate 334). 



'Steel reinforcement 



'Cast iron frame 

 tight cover 



PLATE No. 334 

 SEPTIC TANK AND SIPHON CHAMBER FOR TWENTY TO TWENTY-FIVE PERSONS 



(Farmers' Bulletin No. 1227, United States Department of Agriculture.) 

 Septic tank: length, 6 feet; width, 3 feet 6 inches; depth below flow line, 5 feet 6 inches; W, 8 inches; X, 



2 feet 9 inches; Y, 5 inches; Z, 8 inches. 



Siphon chamber: length, 10 feet; depth, 2 feet 10 inches; width, 3 feet 6 inches; A, 4 inches; B, 4 inches; 



C, 17 inches; D, 2O l / inches. 



