George M. (George Milton) Warren.

Sewage and sewerage of farm homes online

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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 se-
cure 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 26. 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


Farmers' Bulletin 1227.

FIG. 24. Two-chamber septic tank, simple and inexpensive. Constructed of 24-inch
vitrified sewer pipe ; size suitable for 125 gallons of sewage daily (nominally 3 per-
sons). A, House sewer; B, settling chamber, made of one double T branch and one
length of straight pipe, each 3 feet long and 2 feet in diameter, supported by 4 inches
of concrete, all joints made water-tight ; C, submerged outlet, consisting of a metal T
slipped into the sewer-pipe branch ; D, wire screen, JHnch mesh ; E f siphon chamber
made of one T branch 3 feet long and 2 feet in diameter ; F, siphon ; G, 3-inch over-
flow ; H, sewer to distribution field: /, tightcover with lifting- ring: J, concrete pro-
tection around sewer-pipe hubs.

/ Steel reinforcemem

J outlet

~T Settling

distribution field V;^

. 25. Typical two-chamber concrete septic tank. (See table for dimensions and
quantities for different sizes.)

Sewage and Sewerage of Farm Homes.


out the confined air, destroying the balance and causing a rush of
water through the siphon to the sewer. The entire operation is auto-
matic and very simple. The siphons shown are commercial products
made of cast iron; they have few parts and none that move, and the

High water or
Discharge line

Diameter of siphon





























Diameter of outlet..

Drawing depth


Depth to floor

Height above floor



7 1 A


8 3 / 4


N 3 /4

25 3 / 4

Clearance under bell

/nside bottom ofout/et, to discharge line.
Discharge line, to top of wall

Depth of outlet sump ..

Length and width of outlet sump

Diameter of carrier, and minimum
fall in feet per 100 feet

^^^100 fT * +
*2r^\r"-^-^ S= Minimum fall














2 '/2ft.






FIG. 26. Three types of sewage siphon. The table gives dimensions for setting standard
3 and 4 inch siphons ; also the appropriate size and grade of the sewer to carry the
siphon discharge.


whole construction is simpie and durable. The table (fig. 26) lists
stock sizes adapted to farm use. Manufacturers furnish full infor-
mation for setting their siphons and putting them in operation. For
example, take type 2, figure 26: (1) Set siphon trap ( U-shaped pipe)
plumb, making E (height from floor to top of long leg) as specified;

40 Farmers' Bulletin 1227.

(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 26, may be installed readily
in a tank already built by addition of an outlet sump. If properly
set and handled, sewage siphons require very little attention and
flush with certainty. Like all plumbing fixtures the} 7 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 suffi
cient 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 thorn.

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 25 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


mesh strips /Q "wide, ^ |*- 22" ,., f . o- no

about fapound per square foot r^-iri,.?..L-..-.'S '


FIG. -7. Homemade reinforced concrete covers. (1) Slabs placed crosswise permit un-
covering the whole tank for cleaning, but as inspection is somewhat difficult, cleaning
is the more likely to bo neglected; (2) manhole, 18 inches square: cover, 22 by 22 by 3
inches thick, easy to make and to slide or lift from the opening.

concrete and left in place. Sometimes a galvanized wire screen
(J-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 25
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 ob-
tainable from plumbing supply houses, home-made slabs of rein-
forced concrete (see fig. 27), o wooden covers (see fig. 23) may be

Overflow. The purpose of an overflow is to pass .sewage to the dis-
tribution field should the siphon stop working. The overflow (fig.
25) 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

Sewage and Sewerage of Farm Homes. 41

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 25 ; 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 dimen-
sions 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 28. 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.

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 thor-
oughly 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 (ac-
cording 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.

Steel reinforcement. To stiffen the cover slab and guard against
cracking, a little steel should be embedded in the concrete about 1

10 See footnote, p. 17. For more detailed information on form and concrete work the
reader is referred to U. S. Department of Agriculture Farmers' Bulletin No. 481, " Con*
crete Construction on the Live-Stock Farm."


Farmers' Bulletin 1227.

inch above the inside top. For this purpose a strip of heavy stock
fencing is convenient and inexpensive. The line wires should be not

Thickness of division wa//


FIG. 28. Forms for concrete work bow to use them.

1. Make the forms as shown and to the dimensions required by fig. 25 and the table
on p. 37 ; nails to be driven from the inside and left projecting sfor drawing with a claw

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 sub-
merged outlet pipe at the proper height.

5. Block siphon trap and connected branch 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.

less than No. 10 gauge (about -J inch) and the stay wires not less
than No. 11 gauge. The reinforcement should be cut at manholes and

Sewage and Sewerage of Farm Homes. 43

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 J-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 26 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. 20),
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 sun-
light and air free access. It should be located at least 300 feet down-
hill from a well or spring used for domestic water supply. Pref-
erably it should slope gently, but sharp slopes are not prohibitive.
Subsoiling the area is always desirable.

Clay and other compact, impervious soils require special treat-
ment. 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 in-
stances dynamite has been of service in opening up the ground to*
still greater depth. Drainage and aeration should be further pro-
moted by laying tile underdrains, as outlined in figure 19 and shown
in more detail in figure 31.

After the construction work the distribution area 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

44 Farmers' Bulletin 1227.

tile must be so laid that loose dirt will not fall or wash into the open

Different methods of dividing the fltfsh and laying out the distri-
bution tile are shown in figures 29 and 32. Layouts 1, 2, and 3, figure
29, are suitable for flat or gently sloping areas and are planned for
the shallow siphon chambers tabulated on page 37. Layout 4, fig-
ure 29, 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 carpenters 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 pro-
vision 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 be-
tween 3-inch and 4-inch tile the smaller size costs less and is bet-
ter 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. Lay-
outs 1, 2, and 3, figure 29, 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 29 espe-
cially, 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 south-

Sewage and Sewerage of Farm Homes.


* I Oft - /0/X /0/X |

10 ft. -j

FIG. 29. Methods of laying distribution system : Methods 1, 2, and 3 for flat or gently
sloping land; method 4 for steep slopes (see also fig. 32) ; A, direction of slope; B,
contour of field ; C, sewer from tank, preferable size ^ iach, though 4 or 6 inch may
be used, depending on the fall and the size of the siphon (see table, fig. 26) ; D,
V -branch set to divide the flow exactly ; E, reducer, to 4 inches ; F, i bend, 4 -inch; G,
increaser, from 4 inches ; H, incrcascr, 3 to 4 inches ; /, reducer, 4 to 3 inches ; J, dis-
tribution tile, 3-inch ; K, distribution tile, 4-inch.


Farmers' Bulletin 1227.

ern 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 2^ or 3 feet near the Canadian line.
What is better, the tile in all instances may be laid with a 10-inch
cover and in cold weather the runs may be covered with hay, straw,
or leaves weighted down, which may be removed in the spring.

Making the joints of the distribution tile demands especial atten-
tion. For a short distance on the upper end of each run the tile
should be laid with ends abutting; the joint opening should be in-


FIG. 30. Four methods of protecting open joints in distribution lines an all-important
work. Sketches show cross-section and longitudinal views ; the depth from the surface
of the ground to the top of the tile is about 10 inches.

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, alloAvirtg 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.

creased 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 30.
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

Sewage and Sewerage of Farm Homes.


to subsoil and underdrain the area thoroughly, as shown in figure 31.
It is not always possible to run the underdrain in lines between the
distribution lines as shown in figures 19 and 31, 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 con-
tinuous 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
18 or 31.

Figure 32 shows two other methods of controlling the flow on steep
slopes and diverting proper proportions to the several lateral distrib-
utors 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

FIG. 31. Close soils should be deeply subsoiied and underdrained. Porous, well-drained,
air-filled soil is absolutely necessary. A, Subsoiied ground ; B, 3 or 4 inch distribution
tile; c, depth variable with the climate, 1| to 3* feet; D, 4-inch underdrain; 17, depth
such as would prepare land for good crop production, generally 3i to 4 feet ; F, stone
or other coarse material ; Gr, gravel grading upward to coarse sand ; H, loose soil.

this difficulty recourse is had to diverting boxes, of which two types
are shown in figure 32. 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 distrib-
utors head. It will be noted that the laterals enter at slightly dif-
ferent elevations, the two opposite the inlet sewer being the highest,
the next two slightly lower, and the next two the lowest. This stag-
gering of the outlets, in a measure, offsets the tendency of the flow
to shoot across and escape by the most direct route.

Type 2 calls for one or more diverting boxes, according to the num-
ber 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.


Farmers' Bulletin 1227.

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


Plan of Diverting Box


Cross Section of Diverting Box

Cross Section

FIG. 32. Two systems of distribution on steep slopes use of diverting box. A, Direc-
tion of slope ; B, contour of field ; C, 4, 5 or 6 inch sewer from tank ; D, diverting box ;
E, 3-inch or 4-inch distribution tile.

aerated while the other is in use. This procedure is especially de-
sirable where the soil is close and the installation of considerable
size. It adds to the life and effectiA T eness of the distribution area and
permits use of a plant in case it is necessary to repair, extend, or re-
lay 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 de-

Sewage and Sewerage of Farm Homes.


sirable 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 ad-
visable to more nearly double the requirements previously described.
Two simple types of switch are shown in figure 33. The switch
should be turned frequently, certainly as often as is necessary to pre-
vent saturation or bogginess of either area.



Cross Section

Cross Section

FIQ. 33. Two simple types of sewage switch. A, Sewer from tank ; B, switch box ; C,
cover ; D, blade or stop board (in the left-hand box the direction of flow is controlled
by placing the blade in alternate diagonal position ; in the right-hand box the stop

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Online LibraryGeorge M. (George Milton) WarrenSewage and sewerage of farm homes → online text (page 4 of 5)