Popular Science Monthly 



463 



FROM 

 TANK. 



heavy loam soil is used, the discharge cham- 

 ber must be larger and deeper, in order that 

 the discharge interval may be lengthened 

 and the distribution system be given 

 ample time to aerate. If the distribution 

 is in sandy or very porous soil the dis- 

 charge may be more frequent. 



The table of dimensions of septic tanks 

 suggests sizes of settling and discharge 

 chambers and the corresponding siphon 

 sizes to apply to various average condi- 

 tions. The depths of siphon chambers 

 given are the minimum allowable. 



The table is computed on the basis that 

 the inlet and outlet of the settling cham- 

 ber should be placed with their inverts 

 12 in. below the roof of the tank, thus 

 making the depth of sewage in 

 both settling and discharge 

 chamber 12 in. less than the 

 mean inside depth. 



The tank dimensions given 

 are for average cases only and are not 

 standard for all such cases. They are sub- 

 ject to variations to suit local conditions; 

 yet care should be taken not to vary any 

 of the essential dimensions, and not to go 

 below the given minimum depth of the siphon 

 chamber. 



In the illustration Fig. 1, is shown a 

 double-chamber septic tank for a family 

 of six people. Another type of tank for a 

 family of eight people is shown in Fig. 2. 

 These tanks are suited 

 to conditions where 

 plenty of outlet fall is 

 available. A double- 

 chamber tank for a 

 family of six persons is 

 shown in Fig. 3. This 

 tank is suited to flat 

 ground where outlet 

 fall is difficult to ob- 

 tain, as will be noted 

 by the difference in 

 elevation between the 

 floors of the two 

 chambers. For satisfactory operation, a 

 small septic tank should be a size suitable 

 for use by at least six persons. 



The septic tank, although airtight and 

 supposedly watertight, should be located 

 as far from the house and the well or 

 spring as convenience and local surround- 

 ings will permit, thus reducing the danger 

 of pollution or nuisance in case of leakage 

 or improper operation of the system. 



Fig. 6: Cross section 

 of a single tile sew- 

 age disposal system 



The sewer from the house should be of 

 vitrified sewer pipe, usually 4 in. in size, 

 with tightly cemented joints, and should 



GATE CHAMBER 



Fig. 5 : A ground plan for the laying of the 

 tile in a system leading from a sewage dis- 

 posal plant to drain the tanks underground 



be laid to a grade of less than 9 in. per 

 100 ft. Where the fall from the house 

 to the tank is excessive, it is a good plan 

 to lay at least 100 ft. of tile to the mini- 

 mum grade to break 

 up entrance velocity. 

 It is assumed that 

 the farmer has a 

 working knowledge 

 of small concrete 

 structures. The 

 septic tank, prefer- 

 ably of concrete, ^^v-m o o-v^oo-o^i'-v- 

 should be made as ^/^/fe^^'^'og^^ 

 nearly watertight /r/;:^'A\«8"VoV^^/<< 

 as possible. The 







walls should be 6 or 



8 in, thick, the floor 



4 to 6 in. thick, and 



the roof about 6 in. 



thick and reinforced. 



Some means should 



be provided at the 



bottom to facilitate 



the cleaning out of the settled sludge. 



Either the floor may be sloped toward 



Fig. 7: A single 

 tile system with 

 underdrainage tile 



