464 



Popular Science Monthly 



5EWER FROM 

 RESIDENCE 



5ErrUNGTANK 



the inlet-end for this purpose or a pipe 

 with a valve may be installed below the 

 tank, as shown in Fig. 1 and 2. The 

 discharge chamber should be fitted with an 

 outlet, set above the siphon, which will 

 allow the sewage to escape in case the siphon 

 becomes clogged. 



A concrete mixture of 1 part cement to 

 2 or 2]i parts 

 sand and 4 or 5 

 parts of broken 

 stone or gravel 

 should be used 

 in the construc- 

 tion of the tank, 

 It is an excel- 

 lent idea to 

 waterproof the 

 concrete. 



An auto- 

 matic siphon 

 is shown in Fig. 

 4. It operates 

 as follows: As 

 the liquid en- 

 ters the dis- 

 charge cham- 

 ber its weight 

 increases with 

 increasing 

 depth, and the 

 air between the 

 water surface 

 in the bell and 

 the water in the 

 siphon-leg is 

 compressed. As the water outside increases 

 in depth, the compression inside becomes 

 greater until the water outside reaches 

 the drawing or discharge depth for the 

 siphon. Then the inside pressure is 

 sufficient to force the water in the siphon- 

 leg around the bend, instantly relieving 

 the compression. The water from the 

 tank then rushes in to fill up the space 

 which was occupied by the air and starts 

 the siphon, which continues until the out- 

 side and inside pressure are again equal- 

 ized. 



Where the soil is porous or sandy and 

 there is plenty of area available, which is 

 used for no other purpose, the sewage from 

 the septic tank may be discharged through 

 4-in. distribution tile laid on the surface of 

 the ground in gridiron or herringbone 

 fashion. The area necessary is from 4 .SO 

 to 500 sq. ft. for each person served, if the 



DISTRlBUTINS- 

 TROUGH. 



UNDERDRA1N5 



Fig. 8 : A sand filter on a level area with embankments about 

 two feet high that inclose the beds, in which one cubic yard of 

 filtering material is used to each fifty gallons of sewage flow 



soil is very porous or sandy, and the soil 

 should be either tile-drained or have 

 natural underdrainage. 



A better method of disposal is by sub- 

 surface distribution. In this method the 

 tiles are placed in the ground in herring- 

 bone or gridiron fashion, not deeper than 

 14 or 16 in. from the surface of the soil 



to the top of 

 t h e t i 1 e . 

 Ground plans 

 for such sys- 

 tems are shown 

 in Fig. 5. In 

 very porous or 

 sandy soils 1 

 ft. of 4-in. tile 

 per gallon of 

 discharge for 

 each day is suf- 

 ficient. In the 

 heavier loam 

 soils 2 ft. or 

 sometimes 

 moreof4-in.tile 

 for every gallon 

 necessary. A 

 rough esti- 

 mate should be 

 made of the 

 number of gal- 

 lons of sewage in 

 each discharge 

 from the tank 

 and the number 

 of discharges 

 per day. Not less than 35 ft. of 4-in. tile 

 per person should be used in sandy or 

 porous soil and not less than 60 ft. per person 

 in very heavy loams. In average loams 

 300 to 400 ft. of tile are sufficient for a family 

 of six or eight persons. 



Aeration of heavy soils can be effected 

 by the use of coarse cinders or gravel laid 

 in 12-in. to 16-in. layers in the bottom of 

 the tile ditch with the top about 12 in. 

 below the surface. The tiles are laid in 

 these at the usual depth. Such an ar- 

 rangement is shown in Fig. 6. The dis- 

 posal tile should have a fall which does 

 not exceed 1 in. in 50 ft., or the water will 

 rush to the lower end and water-log the soil. 

 The tiles are usually laid about J4 i^- 

 apart and in rows about 15 ft. apart. The 

 latter distance, however, will vary with 

 the porosity of the soil. Where there is no 

 subsurface drainage, artificial drainage 



