Chapter II: Part 2

_F_ shows the use of a pipe jointer for pouring a hot filler. The pipe jointer may be an asbestos or rubber runner or collar or a piece of garden hose clamped around the pipe leaving a small triangular opening at the top. The jointer is pressed firmly against the hub, and any small openings between the jointer and pipe are smeared with plastic clay to prevent leakage of the filler. A clay dike or funnel about 3 inches high built around the triangular opening greatly aids rapid and complete filling of the joint space. The filler may be a commercially prepared bituminous compound or molten sulphur and fine sand. The former makes a slightly elastic joint; the latter a hard unyielding joint. With good workmanship both kinds of joint are practically water-tight and root-proof, and cost about the same as cement mortar joints. The filler is heated in an iron kettle over a wood, coke, or coal fire. It should be well stirred, and when at a free running consistency should be poured with a ladle large enough to fill the joint completely at one operation. As soon as the compound cools the jointer is removed. Sulphur-sand filler is made by mixing together dry and melting equal volumes of ordinary powdered sulphur and very fine clean sand, preferably the finest quicksand. A 5-inch sewer pipe joint requires from three-tenths to nine-tenths of a pound (according to the kind of pipe) of sulphur, worth 3 to 5 cents per pound, and a like quantity of sand. From ½ to 1½ pounds of bituminous filler are required for a 5-inch pipe joint.

_G_ shows section of finished joint.

_H_ shows the use of a pouring ladle in making lead joints in cast-iron soil pipe. This pipe is in lengths to lay 5 feet, and the metal of the barrel is ¼ inch thick. The joint is yarned with dry jute or oakum, as described above, and is poured full with molten, soft, pig lead to be afterwards driven tightly with hammer and calking tools. About ¾ pound of lead for each inch in diameter of pipe is required. Prepared cements of varying composition have proved effective and, as they require no calking, are economical. Among the best is a finely ground, thoroughly mixed compound of iron, sulphur, slag, and salt.

_I_ is a homemade pipe jointer or clay roll for use in pouring molten lead. A strand of jute long enough to encircle the pipe and the ends to fold back, leaving an opening at the top, is covered with clay moistened, rolled and worked to form a plastic rope about 1 inch in diameter. The jointer gives the very best results but must be frequently moistened and worked to keep the clay soft and pliable. The jointer shown in _F_ is frequently used for pouring lead joints.

Obstructions in house sewers are frequent. Among the causes are broken pipes, grade insufficient to give cleansing velocities, newspaper, rags, garbage, or other solids in the sewage, congealing of grease in pipes and main running traps (house sewer traps), and poor joint construction whereby rootlets grow into the sewer and choke it. Good grade and good construction with particular care given to the joints, will avert or lessen these troubles. The sewer should be perfectly straight, with the interior of the joints scraped or swabbed smooth. When the joint-filling material has set, the hollows beneath the hubs should be filled with good earth free of stones, well tamped or puddled in place. It is important that like material be used at the sides of the pipe and above it for at least 1 foot. The back filling may be completed with scraper or plow. No running trap should be placed on the house sewer, because it is liable to become obstructed and it prevents free movement of air through the sewer and soil stack. Conductors or drains for rain or other clean water should never connect with the house sewer, but should discharge into a watercourse or other outlet.

Where obstruction of a house sewer occurs, use of some of the simple tools shown in Figure 20 may remedy the trouble. It is not likely that farmers will have these appliances, except possibly some of the augers; but some of them can be made at home or by a blacksmith, and most of them should be obtainable for temporary use from a well-organized town or city sewer department. The purpose of the several tools shown is indicated in the notation.

=The tank.=--The septic tank should be in an isolated location at least 50 to 100 feet from any dwelling. This is not always possible, because of flat ground, but in many such instances reasonable distance and fall may be secured by raising both the house sewer and tank and embanking them with earth. Cases are known where tanks adjoin cellar or basement walls and the top of the tank is used as a doorstep; in other cases tanks have been constructed within buildings. Such practices are bad. It is difficult to construct an absolutely water-tight masonry tank, and still more difficult to make it proof against the passage of sewer odors.

In Northern States, particularly in exposed situations, it is desirable to have the top of the tank 1 to 2 feet underground, thus promoting warmth and uniformity of temperature in the sewage. In Southern States this feature is less important, and the top of the tank may be flush with the ground. Every tank should be tightly covered, for the reasons above stated and to guard against the spread of odors, the transmission of disease germs by flies, and accidents to children.

Considerable latitude is allowable in the design and construction of septic tanks. No particular shape or exact dimensions can be presented for a given number of people. One family of 5 persons may use as much water as another family of 10 persons; hence the quantity of sewage rather than the number of persons is the better basis of design. Exact dimensions are not requisite, for settlement and septicization proceed whether the sewage is held a few hours more or a few hours less. As to materials of construction, some form of masonry, either brick, building tile, rubble, concrete, or cement block, is employed generally. Vitrified pipe, steel, and wood have been used occasionally.

A plant for use all year round should have two chambers, one to secure settlement and septicization of the solids and the other to secure periodic discharge of the effluent by the use of an automatic sewage siphon. The first chamber is known as the settling chamber, the second as the siphon or dosing chamber. The siphon chamber is often omitted and the effluent is allowed to dribble away through subsurface tile, as illustrated in Figure 16. The latter procedure is not generally advised, but may be permissible where the land slopes sharply or has long periods of rest, as at summer houses and camps.

The septic tanks shown in this bulletin are designed to satisfy the following conditions:

1. Water consumption of 40 gallons per person per day of 24 hours.

2. A detention period of about 24 hours; that is, the capacity of the settling chamber below the flow line is approximately equal to the quantity of sewage discharged from the house in 24 hours.

3. Where a siphon chamber is provided, its size is such that the dose of sewage shall be approximately equal to 20 gallons per person; that is, the capacity of the siphon chamber between the discharge and low-water lines is roughly equal to the quantity of sewage discharged in 12 hours.

A simple one-chamber brick tank suitable for a household discharging 180 to 280 gallons of sewage daily is shown in Figure 21. A small two-chamber tank constructed of 24-inch vitrified pipe, suitable for a household discharging about 125 gallons of sewage daily, is shown in Figure 22. A typical two-chamber concrete tank is shown in Figure 23. Excepting the submerged outlet, all pipes within the tank and built into the masonry are cast-iron soil pipe with cast-iron fittings. Vitrified or concrete sewer pipe and specials are generally used, as they are frequently more readily obtainable and a slight saving in first cost may be effected. Cast iron is less liable to be broken in handling or after being set rigidly in masonry, and the joints are more easily made water-tight. The submerged outlet is midway of the depth of liquid in the settling chamber. The inside depth of the siphon chamber is the drawing depth of the siphon plus 1 foot 5 inches.

The following table gives the principal dimensions with quantities of materials for four sizes of tank as illustrated in Figure 23:

_Dimensions and quantities for septic tanks_

--------+--------+--------+--------------------------------------------
|Quantity| | Settling chamber.
| of |Capacity|
Number | sewage | below +-------+-------+-------+----+-------+---+---
of | in 24 | flow |Length.| Depth.|Width. | W. | X. | Y.| Z.
persons.| hours. | line. | | | | | | |
--------+--------+--------+-------+-------+-------+----+-------+---+---
| Galls. | Galls. |Ft. In.|Ft. In.|Ft. In.| In.|Ft. In.|In.|In.
5 | 180-280| 240 | 4 0 | 5 0 | 2 0 | 6 | 2 0 | 4 | 6
10 | 320-480| 420 | 5 0 | 5 6 | 2 6 | 6 | 2 3 | 4 | 6
15 | 520-680| 620 | 5 6 | 6 0 | 3 0 | 8 | 2 6 | 5 | 8
20 | 720-960| 860 | 6 0 | 6 6 | 3 6 | 8 | 2 9 | 5 | 8
--------+--------+--------+-------+-------+-------+----+-------+---+---

--------+----------+------------------------------------------------
| Quantity | Siphon chamber.
Number |of sewage +-------+--------+--------+----+----+----+-------
of | in 24 |Length.| Depth. | Width. | A. | B. | C. | D.
persons.| hours. | | | | | | |
--------+----------+-------+--------+--------+----+----+----+-------
| Galls. |Ft. In.| Ft. In.| Ft. In.| In.| In.| In.| In.
5 | 180-280 | 5 0 | 2 8 | 2 0 | 3 | 4 | 15 | 18-1/4
10 | 320-480 | 8 0 | 2 8 | 2 6 | 3 | 4 | 15 | 20-1/4
15 | 520-680 | 8 8 | 2 10 | 3 0 | 4 | 4 | 17 | 20-1/4
20 | 720-960 |10 0 | 2 10 | 3 6 | 4 | 4 | 17 | 20-1/4
--------+----------+-------+--------+--------+----+----+----+-------

--------+---------+---------+--------+--------+---------+-------------
|Quantity | | | | |Reinforcement
| of | | | | | in top slab
Number | sewage | | | | | (strip of
of | in 24 |Concrete.| Cement.| Sand. | Stone. | heavy stock
persons.| hours. | | | | | fencing).
| | | | | +-------+------
| | | | | |Length.|Width.
--------+---------+---------+--------+--------+---------+-------+------
| Galls. | Cu. yds.| Bbls. |Cu. yds.| Cu. yds.| Ft. | In.
5 | 180-280 | 3 | 4-1/2 | 1-1/3 | 2-2/3 | 10 | 32
10 | 320-480 | 4-1/4 | 6-1/4 | 2 | 3-3/4 | 14 | 39
15 | 520-680 | 6-2/3 | 9-3/4 | 3 | 6 | 15-2/3| 47
20 | 720-960 | 8 | 12 | 3-1/2 | 7 | 17-1/2| 56
--------+---------+---------+--------+--------+---------+-------+------

=Siphons.=--Reference has already been made to the vital importance of air in sewage filtration. If the spaces within a filter or soil are constantly filled with water, air is excluded, and the action of the filtering material is merely that of a mechanical strainer with its clogging tendency. The purpose of a siphon is twofold: (1) To secure intermittent discharge, thus allowing a considerable period of time for one dose to work off in the soil and for air to enter the soil spaces before another flush is received; (2) to secure distribution over a larger area and in a more even manner than where the sewage is allowed to dribble and produce the conditions of the old-fashioned sink drain--namely, a small area of water-logged ground.

Three types of sewage siphon are shown in Figure 24. In all, the essential principle is the same: A column of air is entrapped between two columns of water; when the water in the chamber rises to a predetermined height, called the discharge line, the pressure forces out the confined air, destroying the balance and causing a rush of water through the siphon to the sewer. The entire operation is automatic and very simple. The siphons shown are commercial products made of cast-iron; they have few parts and none that move, and the whole construction is simple and durable. The table (fig. 24) lists stock sizes adapted to farm use. Manufacturers furnish full information for setting their siphons and putting them in operation. For example, take type 2, Figure 24: (1) Set siphon trap (=U=-shaped pipe) plumb, making E (height from floor to top of long leg) as specified; (2) fill siphon trap with water till it begins to run out at B; (3) place bell in position on top of long leg, and the siphon is ready for service. Do not fill vent pipe on side of bell.

The overhead siphon, type 3, Figure 24, may be installed readily in a tank already built by addition of an outlet sump. If properly set are handled, sewage siphons require very little attention and flush with certainty. Like all plumbing fixtures they are liable to stoppage if rags, newspaper, and similar solids get into the sewage. If fouling of the sniffing hole or vent prevents the entrance of sufficient air into the bell to lock the siphon properly, allowing sewage to dribble through, the remedy is to clean the siphon. Siphons are for handling liquid; sludge if allowed to accumulate will choke them.

=Submerged outlet.=--The purpose of a submerged outlet is to take the outflow from a point between the sludge at the bottom and the floating solids or scum. The outlet in Figure 23 may be readily made of sheet metal by a tinsmith. Wrought iron or steel pipe with elbows or light lead pipe may be used, the pipe being set in the concrete and left in place. Sometimes a galvanized wire screen (¼-inch mesh) is fitted over the inner end to prevent large solids leaving the settling chamber and possibly clogging the siphon or distribution tile. If a screen is used it should be easily removable for cleaning.

=Manhole frame and cover.=--The frame and cover shown in Figure 23 are stock patterns made of cast-iron and weighing about 250 pounds per set. The cover is 21 inches in diameter; it is tight and, on account of its weight, is unlikely to be disturbed by small children. The frame or rim is about 7 inches high and 31 inches in longest diameter. If desired, light cast-iron cistern or cesspool covers obtainable from plumbing supply houses, homemade slabs of reinforced concrete (see fig. 25), or wooden covers (see fig. 21) may be used.

=Overflow.=--The purpose of an overflow is to pass sewage to the distribution field should the siphon stop working. The overflow (fig. 23) is a 3-inch riser pipe with top 3 inches above the discharge line and the bottom calked or cemented into the side outlet of a =T= branch. The run of the =T= branch should correspond with the size of the sewer from the tank to the distribution field. If this sewer is 4-inch pipe, a 4 by 3 inch =T= branch is used, the 4-inch spigot end of the siphon being calked or cemented into the branch, as shown in Figure 23; if the sewer is 5-inch, a 5 by 3 inch =T= branch is used and connected to the siphon with a 5-inch to 4-inch reducer (in vitrified specials the equivalent is a 4-inch to 5-inch increaser); if the sewer is 6-inch, a 6 by 3 inch =T= branch is used and connected to the siphon with a 6-inch to 4-inch reducer.

=Concrete work.=--Before excavation for the tank is begun, two wooden forms should be built for shaping the inside of the settling and siphon chambers. In most instances the ground is fairly firm, so that the lines of excavation may conform to the outside dimensions of the tank, the back of the walls being built against the earth. The forms may be made of square-edged boards, braced and lightly nailed, as shown in Figure 26. The forms should have no bottom. If it is desired to lay the sides and covering slab in one operation, the top of the forms must be boarded over. All pipe and manhole openings should be accurately placed and cut. The faces of the forms may be covered with paper or smeared with soap or grease to facilitate removal later.

1 Make the forms as shown and to the dimensions required by Figure 23 and the table on p. 29; nails to be driven from the inside and left projecting for drawing with a claw hammer.

2. Excavate to lines 6 or 8 inches, as may be required, outside of the forms and to the depths required for both chambers.

3. Pour settling chamber floor and place form thereon.

4 Pour settling chamber walls to level of siphon chamber excavation, inserting submerged outlet pipe at the proper height. 5. Block siphon and short pipes to correct line and grade, and fill with concrete around the trap.

6. Pour siphon chamber floor, and place the form thereon.

7 Continue pouring all walls to their full height, inserting the inlet pipe when the concrete reaches that elevation.

8. Do not remove forms till the concrete is hard; with favorable weather, forms for walls only may be removed in 1 to 2 days; forms supporting a cover slab should remain 1 to 2 weeks.

The ground should next be excavated to the proper depth for placing the floors in both chambers. The settling chamber floor, being the lower, should be placed first. Effort should be made to secure water-tight work, a feature of especial importance where leakage might endanger a well or spring. A concrete mixture of 1:2:4 is generally preferred (1 volume cement, 2 volumes sand, 4 volumes stone). The ingredients should be of best quality and thoroughly mixed. The concrete should be poured promptly and worked with a spade or flat shovel to make the face smooth and eliminate pockets or voids within the mass.[10] Before the settling chamber floor has hardened the form should be set upon the floor and the concrete work continued up the sides. The pipe form for the submerged outlet should be set. When the side walls of the settling chamber have reached the bottom of the excavation for the siphon chamber, the siphon trap with its connecting branch and short piece of pipe should be set to proper line and grade and blocked in position. The floor of the siphon chamber should now be poured and the form for that chamber placed thereon, leaving a 6-inch or 8-inch space (according to the thickness of the division wall) between the ends of the two forms. Pouring of all side walls and the top slab should continue without stop, making the entire structure a monolith.

[10] See footnote, p. 12. For more detailed information on form and concrete work the reader is referred to U. S. Department of Agriculture Farmers' Bulletin 1480-F, "Small Concrete Construction on the Farm."

=Steel reinforcement.=--To stiffen the cover slab and guard against cracking, a little steel should be embedded in the concrete about 1 inch above the inside top. For this purpose a strip of heavy stock fencing is convenient and inexpensive. The line wires should be not less than No. 10 gauge (about 1/8 inch) and the stay wires not less than No. 11 gauge. The reinforcement should be cut at manholes and fastened around manhole openings. If desired a standard wire-mesh reinforcement weighing about one-third of a pound per square foot may be used. Another alternative is to use 14-inch round rods, spacing the crosswise rods 6 inches apart and the lengthwise rods 12 inches apart. Poultry netting should not be used, because of its lightness.

=Sewer from tank to distribution field.=--The length of this sewer depends on the situation of the field and the fall to it. The size of the sewer depends on the fall that can be obtained and the size of siphon. The table in Figure 24 shows the minimum fall at which 4-inch, 5-inch, and 6-inch sewers should be laid to take the discharge of the 3-inch and 4-inch siphons specified. The line and grade should be set in the same manner as for the house sewer (see fig. 18) and the construction should be as specified under that caption.

=Distribution field.=--The distribution field or area is a sewage filter, and its selection and the manner of preparing it largely determine the success of subsoil disposal of sewage. As a rule farm land is not the best filtering material. It is too fine grained and fertile. Its tendency is to hold water too long, to admit insufficient air, to clog when even small quantities of sewage are applied. Hence the distribution area should be of liberal size--on the average 500 square feet for each person served. It should be dry, porous, and well drained--qualities that characterize sandy, gravelly, and light loam soils. It should be devoid of trees and shrubbery, thus giving sunlight and air free access. It should be located at least 300 feet downhill from a well or spring used for domestic water supply. Preferably it should slope gently, but sharp slopes are not prohibitive. Subsoiling the area is always desirable.

Clay and other compact, impervious soils require special treatment. Less sewage can be applied to them, and hence it is well to have the area larger than 500 square feet per person. Clay should be subsoiled as deep as possible with a subsoil plow. In some instances dynamite has been of service in opening up the ground to still greater depth. Drainage and aeration should be further promoted by laying tile underdrains, as outlined in Figure 17 and shown in more detail in Figure 29.

After the construction work the distribution areas should be raked and seeded with thick-growing grass. Grass is a safe crop; its water requirement is high, and it affords considerable protection from frost. Suitable grasses are redtop, white clover, blue grass, and Bermuda grass. The area may be pastured or kept as grass land.

=Distribution system.=--Poor distribution of the sewage and failure to protect the joints of the distribution tile account for most of the failures. Each flush of the siphon should be so controlled that every part of the field will receive its due proportion. The distribution tile must be so laid that loose dirt will not fall or wash into the open joints.

Different methods of dividing the flush and laying out the distribution tile are shown in Figures 27 and 30. Layouts 1, 2, and 3, Figure 27, are suitable for flat or gently sloping areas and are planned for the shallow siphon chambers tabulated on page 29. Layout 4, Figure 27, is suitable for steep slopes. In all four layouts use is made of one or more =V= branches (not =Y= branches) to divide the flow equally among the several lines. =V= branches, sometimes called breeches, should be leveled with a carpenter's level crosswise the ends of the legs, thus insuring equal division of the flow.

The size and length of distribution tile and the spacing of the lines or runs admit of considerable variation in different soils. Water sinks rapidly in gravels and sands, and hence larger tile and shorter length are permissible than in close soils. Lateral movement is slow in all soils, but extends farther in gravels and sands than in close soils. In average soils the effect on vegetation 5 feet away from the line is practically nil.

From these considerations, with the siphon dose 20 gallons per person, it is usually a safe rule to provide 50 feet of 3-inch tile for each person served and to lay the lines 10 feet apart. Such provision gives a capacity within the bore of the tile lines about equal to the siphon dose, and as some sewage is wasted at each joint a reasonable factor of safety is provided. A spacing of 10 feet will, it is believed, permanently prevent the extension of lateral absorption from line to line, provided the area is fairly well drained. As between 3-inch and 4-inch tile the smaller size costs less and is better calculated to taper the dose to small proportions. Four-inch tile is less likely to get out of alignment or to become clogged; a length of 28 feet has the same capacity in the bore as 50 feet of 3-inch.

Good-quality drain tile in 1-foot lengths or second-quality sewer pipe in 2-foot lengths may be used. The lines are generally laid in parallel runs, but may be varied according to the topography. Layouts 1, 2, and 3, Figure 27, for flat or gently sloping land, run with the slope; layout 4, for steep slopes, runs back and forth along the contour in a series of long flat sweeps and short steep curves. The grade of the runs and sweeps should be gentle, rarely more than 10 or 12 inches in 100 feet. In layouts 1, 2, and 3, Figure 27 especially, it is desirable that the last 20 feet of each run should be laid level or given a slight upward slope, thus guarding against undue flow of sewage to the lowest ends of the system.

The runs should be laid no deeper than necessary to give clearance when plowing and prevent injury from frost. Ten inches of earth above the top of the tile is sufficient generally throughout the southern half of the United States and 18 inches generally in the North, but if the field is exposed or lacks a thick heavy growth of grass, the cover should be increased to 3 to 6 feet near the Canadian line. Where frost goes down 5 to 7 feet, it is better to lay the tile at moderate depth and cover the runs with hay, straw, or leaves weighted down, removing the covering in the spring.

Making the joints of the distribution tile demands especial attention. For a short distance on the upper end of each run the tile should be laid with ends abutting; the joint opening should be increased gradually to one-eighth inch and this increased to one-fourth in the last 20 feet of the run. All joints should be protected against the entrance of loose dirt. Four methods are shown in Figure 28. The lower end of each run should be closed with a brick or flat stone; or, what is better, an elbow or =T= branch may be placed on the end and vented above the surface of the ground, improving the flow of sewage, the ventilation of pipes, and the aeration of the soil.

If the distribution tile must be laid in clay or other close, poorly drained soil, special treatment is necessary. A common method is to subsoil and underdrain the area thoroughly, as shown in Figure 29. It is not always possible to run the underdrain in lines between the distribution lines as shown in Figures 17 and 29, but it is a desirable thing to do, as the sewage must then receive some filtration through natural soil.

In some instances it is sufficient to lay the distribution tile on a continuous bed, 8 to 12 inches thick, of coarse gravel, broken stone, or brick, slag, coke, or cinders and complete the refill as shown in Figure 16 or 29.

Figure 30 shows two other methods of controlling the flow on steep slopes and diverting proper proportions to the several lateral distributors laid along the contour of the field. This work can not be effected properly with =T= or =Y= branches; the flow tends to shoot straight ahead, comparatively little escaping laterally. To overcome this difficulty recourse is had to diverting boxes, of which two types are shown in Figure 30. These boxes involve expense, but permit inspection and division of the flow according to the needs. They may be built of brick, stone, concrete, or even wood.

Type 1 consists of a single box, into which all the lateral distributors head. It will be noted that the laterals enter at slightly different elevations, the two opposite the inlet sewer being the highest, the next two slightly lower, and the next two the lowest. This staggering of the outlets, in a measure, offsets the tendency of the flow to shoot across and escape by the most direct route.

1. _A_, Subsoiled ground; _B_, 3 or 4 inch drain tile; _C_, strip of tarred paper about 6 inches wide and extending three-fourths the distance around the tile, allowing sewage to escape at the bottom; _D_, coarse sand, gravel, broken stone or brick, slag, cinders, or coke, the coarsest material placed around the tile (where the ground is naturally very porous and well drained, special filling in the trench may be omitted); _E_, natural soil.

2. Drain tile covered with a board laid flat, leaving the entire joint open.

3. Drain tile laid in stoneware gutter pieces and the joint covered with stoneware caps; gutter and cap pieces are inexpensive commercial products; their radius is longer than that of the outside of the tile, thus leaving open most of the joint space; the gutter aids in keeping the tile in line.

4. Vitrified sewer pipe with hubs facing downhill; the spigot end should be centered in the hub with a few small chinks or wedges.

Type 2 calls for one or more diverting boxes, according to the number of lateral distributors, and readily permits of wasting sewage at widely separated elevations and distances. The outlet pipes enter the box at slightly different elevations, for the reason already stated. With either type, should the outlets not be set at the right elevations, partial plugging of the holes and a little experimenting will enable one to equalize or proportion the discharges.

=Sewage switch.=--The clogging of filters and soils after long-continued application of sewage has been previously referred to. It is, therefore, desirable to arrange the distribution system in two units with a switch between them, so that one area may drain and become aerated while the other is in use. This procedure is especially desirable where the soil is close and the installation of considerable size. It adds to the life and effectiveness of the distribution area and permits use of a plant in case it is necessary to repair, extend, or relay the tile in either unit.

Arrangement in two units does not necessarily mean doubling the amount of tile and the area required in a single field. However desirable that may be, expense or lack of suitable ground will often prevent. With open sands and gravels and the assumed siphon dose of 20 gallons per person, 15 to 20 feet of 4-inch tile in each unit for each person will usually suffice. With more compact soil it is advisable to more nearly double the requirements previously described. Two simple types of switch are shown in Figure 31. The switch should be turned frequently, certainly as often as is necessary to prevent saturation or bogginess of either area.

=A complete installation.=--The general layout and working plans of a complete installation built in 1915-16 are shown in Figure 32. The plant is larger than those heretofore considered, and involves several additional features. The settling chamber below the flow line has a capacity of 1,000 gallons, and on a basis of 40 gallons per person per day would serve 25 people.

For many years sewage had been discharged through two 4-inch sewers to a cesspool in the rear of the house. The proximity of the well made it unsafe, and the overflow of the cesspool dribbled over the low portion of the garden and barnyard, cheating nuisance.

The first step was to make borings with a soil auger in the pasture 400 or 500 feet from the house. The borings showed a heavy clay soil to a depth of about 4 feet, underlaid with a sandy stratum only a few inches in thickness. It was decided to locate the distribution area in the pasture and to aid the seepage of sewage by digging numerous filter wells through the clay to the sandy stratum. Levels were taken and a contour plan prepared to serve for laying out the plant and establishing the grades.

The septic tank is built in one corner of the barnyard, and a 5-inch sewer connects it with the old 4-inch sewers to the cesspool. All sewer-pipe joints were poured with a flexible jointing compound. The settling chamber is of hopper shape at the bottom, and a 4-inch sludge drain with gate provides for the gravity removal of sludge. The lower end of the sludge drain is above the surface of the ground and 9 feet below the flow line. The end is protected by a small retaining wall, and the sludge is readily caught in barrels and hauled out on the land for burial. The outlet is low enough to drain the settling chamber completely. If it is desired merely to force out the sludge, the drain may be brought to the surface under a head of 3 to 5 feet, discharging the sludge into a trench or drying bed, to be applied later to the land. A 2-inch waste pipe about mid-depth of the settling chamber permits drawing off the cleared portion of the sewage to the siphon chamber and from thence through another 2-inch waste pipe into the 6-inch sewer leading to the distribution field.

The 4-inch siphon has a drawing depth of 33 inches, and as the siphon chamber is 4 feet wide by 6 feet long the dose is about 500 gallons. The siphon cost $35. The 6-inch sewer to the switch box falls about 6 inches in 50 feet. The distribution field was thoroughly subsoiled, and about 800 feet of 3-inch tile was laid in each unit. At intervals of 25 feet along the distribution trenches 6-inch holes were dug through the clay stratum with a posthole digger. These holes were filled with stone and constitute the filter wells previously mentioned. All tile lines are surrounded with stone and coarse gravel, and the ground has been trimmed to give a uniform cover of 12 inches. All work was done by day labor in a thorough manner. As the men were doing other work at the same time the actual cost is not known, but it is believed the installation cost about $700.

=Cost data.=--Reliable cost figures are difficult to estimate. Labor, materials, freight, haulage, and other items vary greatly in different localities. The septic tank shown in Figure 21 contains about 1,000 bricks and is estimated to cost $60 complete. The septic tank shown in Figure 23 for 5 persons is estimated to cost $135; for 10 persons, $170; for 15 persons, $240; for 20 persons, $280. In Maryland, in 1916, the cost of installing a septic tank similar to that shown in Figure 23 (for 5 people), including 86 feet of 5-inch house sewer (55 feet of cast-iron pipe passing a well, and 31 feet of vitrified pipe) and 214 feet of second-quality 4-inch sewer pipe in the distribution area, was as follows:

Excavation, labor $7.50
Materials delivered 46.60
Three-inch siphon, including freight 15.75
Construction, labor 28.00
Supervision 5.00
------
Total 102.85

The quotations in the following table will be found useful in making estimates of cost:

_Cost per foot of pipe and drain tile_

(Approximate retail prices, Washington, D. C., February, 1928)

------------------------------------+-----------------------------------
| Size, in inches.
Kind of pipe. +--------+--------+--------+--------
| 3 | 4 | 5 | 6
------------------------------------+--------+--------+--------+--------
| | | |
Extra heavy cast-iron soil pipe | $0.23 | $0.31 | $0.40 | $0.48
Vitrified salt-glazed sewer pipe | .15 | .15 | .22½ | .22½
Clay or shale drain tile | .06 | .07 | .10 | .13
| | | |
------------------------------------+--------+--------+--------+--------

The cost of cast-iron fittings may be roughly estimated as follows; Bends, one and one-half times the price of straight pipe; =T=-branches, two times the price of straight pipe; reducers, average of the prices of straight pipe at each end. The cost of clay bends, =T=-branches, reducers, and increasers may be roughly estimated at four times the price of straight pipe.

=Operation.=--Attention must be given to every plant to insure success. Unusual or excessive foulness should be investigated. No chemicals should be used in a septic tank; garbage, rags, newspaper, and other solids not readily soluble in water should be kept out of sewers and tanks. The plant should be inspected often, noting particularly if the siphon is operating satisfactorily. If scum forms in the settling chamber it should be removed, and the sludge should be bailed or pumped out yearly. Frequently tanks are not cleaned out for three or four years, resulting in large quantities of solid matter going through to the distribution system and clogging it. Clogging may occur in the tile or in the adjacent soil. In either case the tile should be dug up, cleaned, and relaid. In some cases it has been found advantageous to relay the tile between the former lines. When sewage is applied to fairly porous land at the slow rate here recommended and the plant is well handled the tile lines should operate satisfactorily for many years. Liming heavy soils tends to loosen and keep them sweet.

=Field data.=--As a basis for outlining or designing a suitable installation the following data should be known:

1. State, town, and whether in or near an incorporated municipality.

2. Usual number of persons to be served.

3. Average daily consumption of water in gallons.

4. Kind and depth of well, depth to water surface.

5. Character of soil, whether sandy, gravelly, loamy, clay, or muck.

6. Condition of soil as to drainage.

7. Character of subsoil.

8. Character of underlying rock and, if known, its depth below the
surface.

9. Depth to ground water at both house and field where sewage is to be
distributed.

10. Minimum winter temperature and approximate depth to which frost goes.

11. Number and kind of buildings to be connected with the sewer.

12. Number and kind of plumbing fixtures in each building.

13. Whether plumbing fixtures are to be put in the basement.

14. Depth of basement floor below ground.

A plan to scale or a sketch with dimensions showing property lines, buildings, wells, springs, and drainage outlets should be furnished. The direction of surface drainage should be indicated by arrows. The slope of the land (vertical fall in a stated horizontal distance) should be given or if possible a contour plan (showing lines of constant elevation) should be furnished.

GREASE TRAPS

Farm sewage may contain from 10 to 30 pounds of grease and fats per person per year. This grease, originating mainly in the kitchen-sink, hinders septic action and clogs pipes, filters, and soils. Half the grease may be stopped by a septic tank, but the remainder goes into the distribution system, interfering with its action. A grease trap is a device for separating the grease from other wastes. The need for it may be lessened by carefully depositing waste greases and fats with the garbage; but one should always be installed if the kitchen is carelessly managed or discharges quantities of greasy water as at institutions, hotels, boarding houses, and bakeshops.

A grease trap should have several times the capacity of the greatest quantity of greasy water discharged into it at one time, in order that the entering water shall be well cooled and the grease congealed. The solidified grease rises to the surface of the water in the trap and is retained therein. A dishpan of greasy water (2½ to 3 gallons) is the largest quantity likely to be discharged at one time from an ordinary kitchen-sink, hence the grease trap should have not less capacity than 7 or 8 gallons. Figure 33 shows three types of grease traps suitable for farm use. In each the outlet pipe has small clearance at the bottom. This feature, together with the =V=-shaped hopper bottom, tends to create a scouring velocity and thus prevent the accumulation of coffee grounds and other solid wastes in the bottom of the trap. A grease trap should be close to the sink it is intended to serve, but not within the kitchen, on account of objectionable odors when the trap is opened to remove grease. It is good practice to place the trap in the cellar or basement, where it is safe from frost yet close to the source of grease.

GENERAL PROCEDURE

Do not waste money by digging and partly constructing, afterwards seeking information. Prepare a plan and work from it. Get in touch with your county agricultural and home demonstration agents. Advice may be obtained also from extension workers, State agricultural colleges, State and local boards of health, the United States Public Health Service, and the United States Department of Agriculture. Do not guess distances and levels. Use a measuring tape and some type of level--engineer's, architect's, drainage, hand, or carpenter's. Study this bulletin, and design, lay out, and construct in accordance therewith. Remember to: (1) Isolate the septic tank--locate it 50 to 100 or more feet from any dwelling and, if practicable, to the leeward of prevailing summer breezes; (2) locate the cesspool or sewage-distribution field downhill from the well or spring, and, if possible, 300 feet therefrom; (3) select dry, porous, deeply drained ground for disposal of all sewage; (4) do not apply more sewage to a given area of land than can be thoroughly absorbed and oxidized; (5) lay sewers straight and below the reach of frost, ventilate them thoroughly, and make the joints water-tight and root-proof.

Makeshift methods, materials, or devices should be avoided or used sparingly. Do not place a vent pipe in the top of a cesspool or septic tank if near a dwelling. Siphon chamber and siphon may be omitted in those rare instances where it is feasible to discharge into salt water or into a large stream already badly polluted. Disposal of sewage in a running stream should be a last resort. Such practice endangers water supplies downstream, and unless the volume and velocity of flow are good nuisance may be created in the vicinity. Do not neglect inspection and operation. Clean out settling tanks yearly or oftener. All pipe lines below ground should be marked with iron or stone markers to facilitate examination, repair, or extension of the system.

There is a general but erroneous belief that the cost of sewerage is little in the city but almost prohibitive in the country. All personal and Realty properties in one eastern city represent a valuation of $10,382 per home, which pays $355 for sewers outside the cellar wall. An average farm in a Middle West State represents a valuation of $17,259. Is not the farmer justified in the small outlay required to dispose of the farm sewage? Because of the issuance of bonds and the apportionment of sewer assessments for a series of years the city dweller may have his burden distributed over a long period. The farmer does not pay interest on these obligations, and sewer work can be done more cheaply in the country than in the city.

Safe disposal of farm sewage is not a passing fad but a vital necessity. Besides being an asset a good sewerage installation greatly promotes the wholesomeness and healthfulness of the farm. Moreover the benefits are far-reaching, because farm products go into every home, and farm and urban populations mingle freely.

ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE

January 6, 1930

_Secretary of Agriculture_ Arthur M. Hyde.

_Assistant Secretary_ R. W. Dunlap.

_Director of Scientific Work_ A. F. Woods.

_Director of Regulatory Work_ Walter G. Campbell.

_Director of Extension Work_ C. W. Warburton.

_Director of Personnel and Business W. W. Stockberger.
Administration._

_Director of Information_ M. S. Eisenhower.

_Solicitor_ E. L. Marshall.

_Weather Bureau_ Charles F. Marvin, _Chief_.

_Bureau of Animal Industry_ John R. Mohler, _Chief_.

_Bureau of Dairy Industry_ O. E. Reed, _Chief_.

_Bureau of Plant Industry_ William A. Taylor, _Chief_.

_Forest Service_ R. Y. Stuart, _Chief_.

_Bureau of Chemistry and Soils_ H. G. Knight, _Chief_.

_Bureau of Entomology_ C. L. Marlatt, _Chief_.

_Bureau of Biological Survey_ Paul G. Redington, _Chief_.

_Bureau of Public Roads_ Thomas H. MacDonald, _Chief_.

_Bureau of Agricultural Economics_ Nils A. Olsen, _Chief_.

_Bureau of Home Economics_ Louise Stanley, _Chief_.

_Plant Quarantine and Control Lee A. Strong, _Chief_.
Administration_

_Grain Futures Administration_ J. W. T. Duvel, _Chief_.

_Food, Drug, and Insecticide Walter G. Campbell, _Director of
Administration_ Regulatory Work, in Charge_.

_Office of Experiment Stations_ --------, _Chief_.

_Office of Cooperative Extension Work_ C. B. Smith, _Chief_.

_Library_ Claribel R. Barnett, _Librarian_.

U. S. GOVERNMENT PRINTING OFFICE: 1930

For sale by the Superintendent of Documents, ---- Price 10 cents
Washington, D. C.

* * * * *

Transcriber Note

Minor typos have been corrected. Illustrations were moved to prevent splitting paragraphs. Figure 19 was moved adjacent to the directions and specifications on Page 24. Due to space considerations in the text only version, emphasis of column headers were sometimes eliminated and some of the tables were rearranged. Produced from files generously made available by USDA through The Internet Archive. All resultant materials are placed in the Public Domain.