382 SEWERAGE 



and largest plants, where the engines are of the most economical 

 form, and where the plant is specially designed, it costs at the 

 rate of about 5c. for each million gallons lifted 1 ft. For 

 smaller plants, the costs of lifting 1,000,000 gal. 1 ft. are about 

 as follows: 



Capacity of Plant Cost of Lifting 



Gallons per Day Cents 



10,000,000 or more 5 



1.000,000 10 



100,000 15 



Intermediate quantities may be estimated at intermediate 

 proportionate amounts. 



SEWERAGE 



SEWERAGE SYSTEMS 



A storm-water system is a sewerage system that carries storm 

 water only; a separate system is one that carries house sewage 

 only; and a system that carries both storm water and house 

 refuse is called a combined system. 



A storm-water system should be adequate for the prompt 

 removal of the rainfall from the surface during violent storms, 

 including also such animal and vegetable refuse from the 

 streets as will necessarily be removed with the storm water. 

 If this is accomplished, and the drains are located at sufficient 

 depth, efficient drainage will be provided for the subsoil. 



The separate system should be able to carry off promptly 

 from houses all sink, laundry, and closet wastes, without 

 offensive odors, and without interruption. It should keep 

 itself clean, that is, free from deposits; it should not pollute 

 the .soil through which the pipes pass; and it should have 

 an outlet that is without objection. 



The separate system is less costly than the combined system, 

 is more strictly sanitary, and is especially adapted for towns 

 and villages that are built on porous soil that allows the storm 

 water to be readily discharged at convenient outlets. 



