Constructing the Tank Floor and Cover

Con- tinue pouring the walls, truing the top edge with a trowel or block. Since the walls are poured first, some concrete will work out from under them and will spread over the bottom of the hole. It should be tamped and smoothed into place along with the tank floor, whieh is poured im- mediately after the walls. Do not allow the concrete floor to extend any higher than the*bottom of the forms, or the latter cannot be removed readily. Construction of Cover.—Level off the ground nearby and stake on edge, in parallel lines 3 feet 8 inches apart, two 1 x 4 inch boards 8 feet 5 inches long. Cut and nail in position 1x4 inch cross pieces forming four rectangular compartments with inside dimensions 23 inches by 3 lee CauivorNi\ AGRICULTURAL EXTENSION SERVICE [Cr 82 feet 8 inches (fig. 13). Fill the bottom of these spaces with fine damp earth or with sand to a smooth level surface, leaving 3 inches for con- crete. Pour about 34 inch of conerete and immediately place the rein- forcing, which may be heavy hog fencing or three 14-inch steel rods in each slab. Continue pouring the concrete, leaving the slab smooth and leyel with the top edge of the form. . Reintorcemen? 2" square bors, or Fig. 15.—The form for cover slabs. Removing Yank Forms —aAfter the conerete has taken its initial set (usually within one hour), the 1x2 ineh strips (G, fig. 5) at the four corners may be tapped lightly with a hammer and drawn out. Their re- moval tends to prevent the cracking of the concrete at the corners. When the concrete has set 16 to 24 hours, the forms may he taken out. First remove the 1 x 6 inch hanging boards and the cross braces EZ, then the 2x3 inch corner studding B by prying them inward and drawing nails C. Next, remove the end panels. The side panels may be lifted out intact, care being taken not to break the concrete around the edges of the grooves into which the ends of the baffle hoards are to be inserted. Re- move the 6 x 6 inch boxes from the wall. Curing the Concrete——The concrete should not be permitted to dry rapidly. After it has taken its initial set (usually within one hour) the exposed surfaces may be covered with wet sacks until the forms are re- moved (usually 16 to 24 hours for the tank). After removing the forms, cover the tank and keep it wetted for several days. The cover slabs may be protected with wet sacks for a few hours and then kept wet for one week by means of wet earth or by flooding. A Sepric Tank vor Parm Tomes 15 Completing the Tank.—Point up any porous areas with a mortar made of equal parts of fine sand and cement. Insert the outlet Y braneh in position as shown in figure 2, using sand-cemeut mortar to secure a water-tight joint in the wall. The upper branch of the Y should be plugged with mortar, except for a small vent at the top. The 2 x 10 inch baffle boards should be fitted loosely in the grooves. A small amount of mortar in the grooves at the ends of the top boards will prevent them from floating when the tank is filled with sewage. The sewer pipe from the house projects 2 inches into the tank; it should be mortared in place. The cover slabs may he placed in position after being cured for at least one week and should be installed right side up—that is, with the reinforcing steel near the bottom. Unless the tank is covered with sev- eral inches of dirt, the cover slabs should be sealed with a lean mortar so that the slabs may be more readily removed. A proportion of 1 part cement to 6 parts of sand is recommended. Connecting the Tank.—The sewer pipe leading from the house to the septic tank should be laid to a grade of not less than 14 inch to the foot and embedded firmly in the ground. Although cast-iron pipe with tight- ly leaded joints is recommended, vitrified clay sewer pipe with ce- mented joints may be used between the house foundation and the tank. To clean out any mortar that might obstruct the inflowing sewage, a swab made from a piece of burlap on a stick should be run through each length of pipe after the joint is cemented. The plumbing fixtures and the sewer line should be installed and vented in accordance with standard sanitary plumbing practice. Neither a trap in the sewer line between the house and the septic tank nor a vent in the septic tank is required. A clean-out plug, as shown at A, figure 1, is recommended. FINAL DISTRIBUTION OF EFFLUENT The effluent from the tank may be utilized for the subirrigation of al- falfa, berries, or trees, and for vegetables which are cooked before eat- ing or which, if eaten raw, do not come into contact with the ground. The location of the disposal area depends upon local conditions. The tank should not be near a well or spring nor in the ground where water may stand at or near the surface; nor should it be emptied into a stream or open ditch. Trees, vines, or shrubs may usually be grown to advantage in the disposal area, for the effluent serves the plants through subirri- gation. In general, under California conditions, the roots aid in the op- eration of the disposal s. arely plug the drainage line. 16 CauirorNiA AcricutturaL EXrension SERVICE [Cir. 82 A vitrified sewer pipe, at Jeast 6 feet long, with cemented joints is used. to carry the effluent from the tank into the subsurface drain line. A satisfactory type of drain line is au inverted V-trough, laid at a grade of 1 inch in 10 feet, on 6 inches of rock or gravel 34 to 114 inches Fig. 15.—View of V-trough in trench, Joints should be staggered as at A and B, in size, back-filled with similar material and covered with earth (figs. 14 and 15). Use at least 10 feet of trough per person up to 100 feet. If addi- tional length is required, branch lines are recommended. The trough may be made of a 2 10 inch and a 2x 12 inch heart com- mon grade redwood or preservative-treated lumber, or of half sections of 12-inch concrete pipe (figs. 16 and 17). A Septic Tank ror Farm Homes 17 ‘The vitrified sewer line from the tank should extend at least 6 inches into the trough (B, fig. 1). The opening between the sides of the trough and the pipe should be filled with gravel and mortar to prevent the Vig. 17,—View of half-section concrete pipe in trench. entrance of dirt or gophers, and the extreme end of the trough should be closed with a sufficient amount of gravel to prevent gophers from en- tering (C, fig. 1). Placing the Tank in Operation —aAfter all cemented joints have ‘set firmly, run 150 to 200 gallons of water into the tank; it is then ready for use, The addition of a “starter” or of bacteria i s not necessary. 18 Carmorni Acricuurursr EXTENSION SERVICE [er, 82 MATERIALS REQUIRED ‘The materials necessary for a septic tank 8 feet wide, 4 feet deep, and 7 feet long, recommended for 4 to 7 persons, are as follows: Concrete Materials: 2 eubie yards crushed rock *% inch to 1 inch in size, Jeubie yard sand. 12 sucks cement. (If erushed rock is not available, 2 cubie yards of clean, well-graded gravel, suitable for good conerete, may he substituted for the rock and sand.) Tile 1 y itrified single-braneh Y sewer tile, size 4-inch, itrified bell-neck sewer tile,5 size 4-inch, Drainage Line: 2” 10" and 2” x12” heart common grade redwood or preservative-treated lumber, or half section of 12-inch conerete pipe. 1% eu. ft. of %-ineh to 13-inch rock for each foot of drainage line. 1 pound 20d nails for each 25 feet of trough. Baffle Boards: 3 pes. 2” 10" x 10’ rough common redwood or eedar; 6-inch and 12-inch widths may be substituted if 10-inch is not available. Jover Forms (common lumber surfaced one side) : 3 pes, 1” x 4” x 12’, Forms (common limber surfaced one side) : Side walls, 9 pes. 1” x 6” x 14", End walls and braces, 6 pes. 1” x 6” x 12’; 2 pes. 1” x 6” x 8". Hanging boards and boxes, 1 pe. 1” x 6” x Baffle cleats and corner strips, 3 pes. 1" x2” < 12’, Long and center studding, 2 pes, 2” x 4” x1 Corner studding, 1 pe. 2” x 3” x 16’. Nails: 2 pounds 8d common wire nails. 2 pounds 6d box nails. Amounts of sewer tile and drainage line not given, as local conditions govern quantity required. A Sepric Tank ror Farm Homes 19 MAINTENANCE OF THE SEWERAGE SYSTEM Close attention to details of construction reduces the possibility of future annoyance with the septic tank sewerage system. Use of Disinfectants—Although large amounts of disinfectants or cleaning agents are detrimental to the bacterial activities in the tank, moderate amounts may be used. Grease Traps.—A grease trap need not be installed, provided waste fats and grease from the kitchen sink are deposited with the garbage. It may, however, be desirable if an excessive amount of greasy water is dis- charged into the tank. It must be frequently cleaned to prevent its be- coming a nuisance. For design of such traps see Farmers’ Bulletin 1227.° Stoppage of Sewage in the System—The most common complaint concerning sewage disposal systems is that waste water | ‘s the plumb- ing fixtures slowly, or that toilets overflow. This trouble is caused by stoppage in the pipe, tank, or drain line. To locate and remedy it, try the following procedure : Open drain line near tank. [f, when the line is opened, water rushes from the drain line, the trouble is in the drainage system. If the soil around the line is saturated along the length of line (not because of natural high water table), the drain is plugged, or more drain line is needed. Tf there is no rush of water when the line is opened, the stoppage is at the inlet of the tank or in the sewer line between the house and the tank. Remove the second cover slab from the inlet end of the tank. Remove the scum from in front of the inlet baffle. Probe around the inlet. If the stop- page is not thus removed, it is in the sewer line. To correct this, run heavy wire, a rod, or a hose with nozzle jetting water, through the sewer line. If there are no clean-out plugs in the sewer line, break a joint to gain entrance. After the line is cleaned, repair the broken joint with mortar. Four-inch drain tile has been used for the drainage line in many dis- posal systems. In time the soil about the joints of the tile becomes im- pervious. In ease this difficulty oceurs frequently, the drain pipe should be relaid in a bed of coarse gravel; or the open-bottom drain line de- scribed in this circular should be substituted for the 4-inch tile line. Cleaning the Tank.—An investigation of the performanee of septic "6 Warren, George M. Sewage and sewerage of farm homes. U. 8, Dept, Agr. Farm- ers’ Bul, 1227:54. 1922, 20 CanirorNiA AGricuLTuRAL Exrension SrrvICE [Crr. 82 tanks that had been in use for three to ten years was made by the au- thors in 1929 and 1930. The results of this study, which covered the ma- jor portion of California, indicated that sludge accumulated in the bottom of the No. 1 tank at the rate of about 1 inch per person per year. Beeause of this accumulation of sludge the capacity of the tank is grad- ually diminished and inereasing quantities of sludge are discharged into the drain line. This, in time, will cause stoppage of the drainage system. On the basis of this investigation it is reeommended that the No. 1 tank described in this circular be cleaned at about 18 person-years’ use —that is, in three years if 6 persons are in the household, or six years if but an average of 3 persons. For the No. 2 tank, 27 person-years’ use is recommended prior to cleaning; for the No. 3 tank, 36 person-years’ use. To clean the tank, take off the two center cover slabs. Remove the seum or mat with a shovel. The liquid and a portion of the sludge may be removed by a pump if the contents are agitated during pumping. Al- lowing water to flow into the tank aids in pumping. Bailing the liquid is often the practical method; remove about 200 pailfuls or 470 gallons. Disposal of the contents to prevent nuisance is simple. Bury the scum and run the liquid into a trench that can be filled in after a few hours. 18m-2,'34 REGULATIONS OF THE STATE BOARD OF HEALTH GOVERNING USE OF SEWAGE FOR CROP IRRIGATION PURPOSES RULE 3. Settled or Undisinfected Sewage Effluents. Effiuents of septic tanks, Imhoff tanks or of other settling tanks, or partially disin- fected effluents of sprinkling filters or activated sludge plants or sim- ilar sewages, shall not be used to water any growing vegetables, garden truck, berries, or low-growing fruits such that the fruit is in contact with the ground, or to water vineyards or orchard crops during seasons in which the windfalls or fruit lie on the ground. Such sewage, effluents or any sludge or screenings shall not be permitted in ditches or pipes which may be used to irrigate vegetables, garden truck, berries, or low-growing fruit. Nursery stock, cotton, and such field crops as hay, grain, rice, alfalfa, sugar beets, fodder corn, cowbeets, and fodder carrots may be watered with such settled or undisinfected or partially disinfected sewage efflu- ents provided that no milch cows are pastured on the land while it is moist with sewage, or have access to ditches carrying such sewage. AMENDMENT JANUARY 2, 1934: However, such sewage may be used for irrigating growing vegeta- bles grown exclusively for seed purposes in fields where crops are raised and watered not in conflict with this rule.