130 DAIRY AND FARM SEWAGE 



wet must be carefully under-drained so as to allow the surplus 

 water to be drained from the surface. This method of disposing 

 sewage is objectionable from the standpoint that the sewage flows 

 on the surface and animals crossing such fields may carry sewage 

 on their feet, and if there are any disease germs in the sewage it 

 may be carried from one place to another. 



The safest method is subsoil irrigation. This consists of a 

 system of underground porous tile, laid in the manner shown in 

 Fig. 4, so as to allow the sewage to seep through the tile. The tile 

 are connected directly with a septic tank and laid so as to leave 

 approximately one-eighth of an inch between each tile in order to 

 allow the sewage to seep through the tile into the soil. The main 

 line should consist of a five-inch tile, depending somewhat upon 

 the sewage. If a great amount of water is used with sewage, 

 four-inch tile may be used. The lateral drains may be four-inch 

 tile, or if the main drain is a four-inch tile the laterals may be 

 three inch. Nothing smaller than a three-inch tile should be used 

 for this purpose. 



For irrigation purposes tile should be laid from eight to sixteen 

 inches beneath the surface of the ground, with a gradual incline 

 of one or two inches for every one hundred feet. The depth to 

 which these tile should be laid depends on the nature of the soil. 

 There should be two systems for each septic tank. One of these 

 systems should be laid below the frost line for winter sewage dis- 

 posal, while the one laid shallow is used for summer disposal. By 

 this method the sewage which is so objectionable on the dairy 

 farm or in the creamery is removed and is used for irrigating and 

 fertilizing purposes. 



This subsurface method of sewage irrigation is particularly 

 profitable for intensive farming, and horticulture. The author 

 knows of a number of instances where in one year such a system 

 has paid for itself by the increased crop production which resulted 

 from irrigating and fertilizing the soil. It is authentically stated 

 that a horticulturist in Ohio has grown enough berries on his 

 irrigated and fertilized soil in one year to pay for three such sew- 

 age disposal plants. 



CONSTRUCTION OF A SEPTIC TANK 



There are numerous ways for building septic tanks. Some of 

 these are shown in Figs. 5, 6, 7, and 8. Such tanks may be built 

 of any tank material, but for durability it is preferable to con- 

 struct them of brick, stone, or concrete. The partitions may be 

 built of concrete or wood. It is generally advisable to build them 

 of concrete if convenient to do so. The tank should be built as 



