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Title: USDA Farmers' Bulletin No. 1950 - Sewage and Garbage Disposal on the Farm
Author: Simons, J. W., Rocket, J. W.
Language: English
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*** Start of this LibraryBlog Digital Book "USDA Farmers' Bulletin No. 1950 - Sewage and Garbage Disposal on the Farm" ***
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SEWAGE and
GARBAGE
DISPOSAL
on the
FARM
[Illustration]
FARMERS' BULLETIN No. 1950
U.S. DEPARTMENT OF AGRICULTURE
This Bulletin is a guide to up to-date methods for the sanitary
disposal of sewage and other household and farm wastes. It tells how
to construct satisfactory sanitary facilities and how to maintain them
and gives special attention to the questions on sanitation asked most
frequently by farm people.
Solutions to all problems cannot be given here, and often advice
must be sought from local sanitary officials. Many county and State
health departments furnish advice and copies of local regulations and
sometimes provide inspection service. Where there are no specific local
requirements, this bulletin may be accepted as a guide to safe practice.
Issued March 1944
Washington, D. C. Revised June 1946
SEWAGE AND GARBAGE DISPOSAL ON THE FARM
By J. W. Rocket, _assistant agricultural engineer_,[1] and
J. W. Simons, _associate agricultural engineer_, _Division of
Farm Buildings and Rural Housing, Bureau of Plant Industry, Soils, and
Agricultural Engineering, Agricultural Research Administration_
[1] The senior author prepared the preliminary draft, and the junior
author completed the bulletin.
Contents
Page
Characteristics of sewage 1
Protection of water sources from household wastes 2
Septic-tank systems 2
Operation of a septic tank system 2
Selecting the site 4
The house sewer 4
The septic tank 8
Building a concrete tank 11
The effluent sewer 13
The disposal field 13
Disposal methods in tight or wet soils 14
Care and maintenance of septic tanks 17
Effect of drain solvents and other materials 17
Protection against freezing 17
Septic-tank troubles 18
Grease traps 18
Disposal of drainage from fixtures other than toilets 19
Cesspools 20
Privies 21
Care, and maintenance 22
Chemical closets 24
Disposal of garbage and trash 25
TO INSURE healthful living, domestic wastes must be disposed of.
Primitive wanderers and too often present-day tourists deposit their
wastes promiscuously and move on when the surroundings become foul.
This is impractical in built-up communities. Therefore, in most cities
and in some rural areas sanitary codes regulate the disposal of wastes.
CHARACTERISTICS OF SEWAGE
Household sewage ordinarily consists principally of human excrement,
toilet paper, garbage, dish water, and other wash water from the
various plumbing fixtures and floor drains.
Many kinds of bacteria, at times disease-producing ones, are contained
in the discharges from the human body. Epidemics of typhoid fever,
dysentery, diarrhea, cholera, and other water-borne diseases may
result from the pollution of the water supply with sewage. Pollution
is carried by water moving underground, as well as by water flowing
on the surface. This is especially true in limestone regions, where
underground channels and rock crevices permit water to flow for
considerable distances with little filtering action. Sewage used for
fertilizing or irrigating crops[2] may contaminate vegetables or the
udders of cows and thus spread disease. Anthrax, cholera, and parasitic
worms may be present in the surface drainage from fields and barn lots.
It is wise to regard all sewage as dangerous and to dispose of it
promptly in a sanitary manner, so that disease germs will not pollute
the water supplies or be spread by flies, animals, or man.
[2] This subject is discussed at length in Technical Bulletin 675,
Sewage Irrigation as Practiced in the Western States.
PROTECTION OF WATER SOURCES FROM HOUSEHOLD WASTES
Under most farm conditions a safe place for the disposal of wastes
is in the upper 3-foot layer of soil, where the action of bacteria
tends to render it harmless. Tile disposal fields, such as are used
with septic tanks, and earth-pit privies accomplish this if the water
table remains several feet below the surface and if the location is
remote from water supplies. Cesspools and other types of pits do not
ordinarily confine contamination to their immediate vicinity and are
not recommended except for special conditions.
Sewage or other wastes discharged into abandoned wells or other pits
that reach to the water table or below it are almost certain to
contaminate the ground water.
It is generally poor practice, and often illegal, to discharge wastes
into surface streams. Streams do not necessarily purify themselves
in 50 feet, 100 feet, or some other stated distance, as is commonly
believed. They do tend to purify themselves over long distances through
the action of sunlight, aeration, and other factors but may not be
safe for domestic use for many miles below the source of pollution.
Clear, sparkling water is not always safe drinking water. Streams in
agricultural communities are subject to many sources of pollution and
they are likely to become more contaminated as they merge into larger
streams.
SEPTIC-TANK SYSTEMS
Septic-tank systems, if installed and maintained properly, provide the
most sanitary method of sewage disposal for farmhouses equipped with
running water.
Ground water or rock close to the surface, lack of sufficient fall for
the sewage to flow by gravity, and too small an absorption area for the
effluent limit the satisfactory operation of a septic tank. When these
conditions exist, special advice should be sought from a competent
local sanitary authority. Adverse soil conditions can be overcome if
sufficient fall and space are available.
The five essential parts (fig. 1) of a septic-tank system are (1)
the house sewer; (2) the septic tank; (3) the effluent sewer; (4)
the distribution box; and (5) the disposal field. In special cases a
grease trap (see fig. 11, p. 19) is added. To facilitate inspection and
repairs it is good practice to keep in the house a chart showing the
location of the tank and other parts of the system.
A septic tank does not necessarily purify the sewage, eliminate odor,
or destroy all solid matter. Its purpose is to condition the sewage or
domestic waste by bacterial action, so that it can be disposed of in a
more satisfactory manner.
[Illustration: Figure 1.--A septic-tank system.]
OPERATION OF A SEPTIC-TANK SYSTEM
In a septic-tank system the sewage flows by gravity from the farmhouse
through the sewer into the tank, where it should remain at least 24
hours. While passing through the tank the solids are acted upon by
anaerobic bacteria, which work only in the dark and where there is
little air. The heavy particles settle to the bottom as sludge, the
lighter particles float as scum, and the remainder passes out of the
tank through the effluent sewer to the disposal field. The gas released
in the process escapes through a vent provided either in the =T= to the
house sewer or the effluent sewer.
A tank that is too small may fill up with solids in a short while,
because sufficient time is not allowed for breaking them down by
fermentation, or the sewage may be pushed right through into the
disposal field and clog it.
The effluent may contain even more disease germs than the original
sewage, and though it may be as clear as spring water it is far from
pure and may cause foul odors if discharged or allowed to pool on the
surface of the ground.
The final disposition of the effluent into the upper layer of the soil
exposes it to the action of aerobic bacteria. These bacteria, unlike
those in the tank, need air and cannot work in saturated soil or live
much more than 3 feet below the surface of the ground. The "living
earth," or upper stratum, teems with these bacteria, which convert the
dangerous sewage and disease germs into harmless matter and thus tend
to purify the effluent if it remains long enough in the top layers of
soil before seeping into the subsoil and thence to the ground water.
Effluent discharged deep in the soil does not receive the benefit of
this purifying action.
Several types of septic tanks are in common use. The one described in
this bulletin is the single-chamber type, which can be built with or
without siphon. This should meet all average farm needs where there
are not more than 16 members in the household. It would be advisable
to consult the authorities of the State agricultural college or local
health department as to their recommendations because frequently local
conditions and larger establishments require special installations.
SELECTING THE SITE
First install the tile disposal field where there will be least danger
of polluting water supplies, at least 100 feet from water sources if
possible and always at a lower surface elevation. This is of greatest
importance. Even though selecting a more distant location would result
in greater initial cost, it would be a good investment as protection
against diseases that might result from pollution of water sources.
The site should slope away from the house and away from the source of
water. Gentle unshaded slopes free of trees or shrubbery are best.
Root-free locations are important because the open-jointed tile cannot
be "rootproofed." Porous, well-drained, gravelly, or sandy soil allows
greater purification. Do not have the disposal field in vegetable
gardens, under roadways, in swampy land, in muck soils, or in areas
having rock substrata sloping toward the water supply. Allow sufficient
area, where available, to enlarge the field later if needed.
The septic tank may be close to the house, but a more distant site
would reduce the likelihood of odors if leakage occurs. The tank should
also be kept 50 feet or more from any source of water supply and at a
lower elevation. It should not be placed under driveways, pavements, or
flower beds, as these would make it not readily accessible for periodic
inspection. Care should be taken to insure that surface drainage from
the area around the tank will not reach the vicinity of the water
supply.
THE HOUSE SEWER
Material
Vitrified salt-glazed clay or well-made concrete sewer pipe and
cast-iron soil pipe are the standard materials for house sewers on
farms. Asphalt-impregnated fiber pipe, of a type designed especially
for house sewers, appears to be satisfactory for this purpose.
Cast-iron soil pipe with leaded joints should be used when the sewer is
within 50 feet of a well or suction line from a well, within 10 feet
of any drinking-water supply line under pressure, within 5 feet of
basement foundations, or when laid beneath driveways with less than 3
feet of earth covering the pipes. When within 15 feet of large trees or
shrubs, the sewers should have root-tight joints.
Size
For house sewers, 4- and 6-inch pipes are generally used. Where a
4-inch pipe is used, cast-iron is commonly recommended. Grades with
little fall require larger pipes. The large sizes are also less liable
to become clogged. Clay pipe is made in pieces 2 or 2-1/2 feet long,
whereas fiber-pipe sections are 4 feet long and cast-iron pipe 5 feet
long, so that there are fewer joints. The minimum number of joints is
desirable, as there is less danger of stoppage.
Alinement
Run the house sewer in a straight line and avoid bends whenever
possible. Slight changes in direction may be made with one-sixteenth or
one-eighth bend fittings. For sharper changes of direction a manhole or
distribution box may be used. Changes in direction of more than 45 are
not recommended unless a manhole is provided. Clean-outs are desirable
within 5 feet of the septic tank where tanks are placed more than 20
feet from the building and the sewer line is not buried deeper than 4
feet.
Establishing Line and Grade
The trench for laying the sewer is usually dug after the septic-tank
excavation has been completed and the elevation of the tank inlet
determined. A simple method of setting guides for the excavation is
illustrated in figure 2.
Digging the Trench
Start digging the trench at the tank end, so that rain or seepage will
have an outlet. Rounding the bottom of the trench to the shape of the
pipe and hollowing out basins for the "bell" ends allows the pipe to
rest firmly throughout its full length, permits full calking of joints,
and relieves the strain on them.
Laying the Pipe
Begin laying the pipe at the tank with the bell end uphill. Joints in
clay-tile pipe are commonly made with portland cement mortar or grout.
Where root-proof joints are essential, sulfur-sand compounds may be
used or copper rings provided and used with cement-mortar joints.
Asphalt-mastic compounds, however, are more satisfactory. For cast-iron
soil pipe, lead is the standard joint material.
After the hub is pushed into the bell, oakum (or old hemp rope) is
packed with a calking iron or a piece of wood (fig. 3, _A_.) solidly
and evenly in the joint to a depth of about half an inch to center the
hub end in the bell and to keep the joint filler from getting inside
the pipe. Oil, grease, or dirt on the joint surfaces should be removed,
as it will prevent joint material from sticking. Figure 3 shows the
different jointing methods.
[Illustration: Figure 2.--Establishing grade for sewer. _A_,
2- by 4-inch stakes are set each side of the trench at convenient
distances _a_, _b_, _c_, and _d_. Then a board is nailed horizontally
on the stakes at _d_ at a convenient height above the bottom of the
trench, that is, the bottom of the sewer leaving the house. A board is
nailed likewise to the stakes at a the same height above the inlet to
the tank that _d_ is above the bottom of the trench. Similarly, boards
are set at _b_ and _c_ by sighting from _a_ to _d_ so the tops of the
intermediate boards will be in line. _B_, The exact grade of the sewer
is obtained by measuring from the grade cord with the 1- by 1-inch
stick, shown in detail. The length of the stick must equal the height
of the board above sewer at _d_.]
Bituminous, sulfur-sand, lead, and other commercial joint compounds are
poured while hot into the joint from a ladle (fig. 3, _F_), and when
the work is well done they form a joint that is practically root-proof.
They are more expensive than cement mortar.
For molding hot compounds, a clay dike, or funnel, built about 3 inches
high around the triangular opening at the top of the jointer greatly
aids in the rapid and complete filling of the joint space. A hot joint
must be poured continuously, otherwise a seam may develop between
successive pourings.
Bituminous compounds make a slightly elastic joint. A joint in 4-inch
pipe requires about 3/8 to 1/2 pound of compound and in 6-inch pipe
about 1 to 1-1/2 pounds.
Sulfur-sand joints are hard and inelastic. The compound is made by
mixing together equal volumes of ordinary powdered sulfur and very
fine clean sand, preferably the finest quicksand, and then heating
the mixture until the sulfur melts. A 4-inch joint takes about 3/4
pound and a 6-inch joint about 1-7/8 pounds of the mixture. Commercial
sulfur-joint compounds also are available.
[Illustration: Figure 3.--Jointing sewer pipe. _A_, Using
calking iron to force packing into joint. _B_, Making joint with 1:2
portland cement mortar. Use only enough water to dampen the mix. Recalk
after half an hour, to close shrinkage cracks. _C_, The completed
joint. Wrap finished joint with cloth and keep dampened, to aid
curing. _D_, Joint made by pouring 1:1 Portland cement grout of creamy
consistency into a form. This type of joint is not feasible unless the
metal forms shown are available. _E_, Use of asbestos runner clamped
around pipe, for pouring hot joint. _F_, Clay roll used in place of
asbestos runner. _G_, A completed bituminous joint. _H_, Use of swab,
to remove any joint material forced through to inside of pipe.]
Soft pig lead or old scrap lead is suitable for lead joints on
cast-iron pipe. About 3/4 pound per inch of pipe diameter is generally
required for each joint. The lead is hot enough to pour when it begins
to char the paddle used to skim off the impurities. When it cools it
must be calked tightly to take up shrinkage. The calking should be
uniform around the entire joint and should stop when the lead is tight.
Heavy pounding or continued calking may crack the bell of the pipe.
It is easier to get good, joints when the pipe is in a vertical
position. Therefore, two lengths of pipe are frequently joined and are
then laid as a single unit in the trench. In using terra cotta pipe,
this procedure may be followed only when the joint is made with a
mastic compound. Cement-mortar joints cannot be used in such cases.
Before filling the trench, the sewer should be tested to detect
possible leaks. Earth free from rubbish and large stones should then be
tamped around and about 1 foot above the pipe.
THE SEPTIC TANK
Flow Through the Tank
Slow, undisturbed flow through the tank is necessary for the separation
of solids and liquids and for bacterial action. Submerged inlets
and outlets or baffle boards reduce disturbance. A submerged outlet
prevents scum from passing out with the effluent.
The single-chamber tank without a siphon, shown in figure 4, is easy
to build, inexpensive, and entirely satisfactory in most instances. In
very tight soils or for large installations a siphon and sometimes two
chambers are advisable.
Size
The tank should be large enough to retain the sewage at least 24 hours.
The size should be determined by the largest number of persons that may
live in the house, rather than by the number actually living there at
the time the tank is built. The additional cost of a large tank over a
small one is relatively little. If there is any question as to which
of two sizes should be built, it is wise to choose the larger. The
dimensions recommended in the table in figure 4 are based on an average
production of 50 gallons of sewage per person per day.
Unusually large quantities of sewage call for a tank of large capacity.
In village and suburban homes where there is less food preparation
than on farms and where the number of persons is more or less fixed,
slightly smaller sizes will serve. In no case should the capacity of
the tank below the flow line be less than 500 gallons. A tank length of
two to three times the width should be maintained, and it is advisable
to provide a depth of at least 4 feet below the flow line.
Allow about 1 foot of "freeboard," or air space, above the flow line
for the accumulation of gases. This space is generally vented through
the soil stack of the house.
A siphon (fig. 5) with a dosing chamber is not considered necessary
for a farm septic tank except for large installations (1,000 gallons
or more), for those in tight soils, and where the disposal field is
limited.
[Illustration]
+---------------------------------------------------------------------------+
| CAPACITIES, DIMENSIONS, AND CONCRETE MATERIALS |
| FOR SEPTIC TANKS SERVING INDIVIDUAL DWELLINGS |
+---------+--------+--------------------------------+-----------------------+
|_Maximum |_Liquid |_Recommended inside dimensions_ |_Materials for concrete|
|number of|capacity+-------+--------+-------+-------+ 1:2-1/2:4 mix_ |
|persons |of tank |_Width_|_Length_|_Liquid|_Total +-------+-------+-------+
|served_ | in | | | depth_| depth_|_Cement|_Sand |_Gravel|
| |gallons_| | | | | sacks_| cubic | cubic |
| | | | | | | | yards_| yards_|
+---------+--------+-------+--------+-------+-------+-------+-------+-------+
|4 or less| 500 | 3'-0" | 6'-0" | 4'-0" | 5'-0" | 16 | 1-1/2 | 2-1/2|
+---------+--------+-------+--------+-------+-------+-------+-------+-------+
|6 | 600 | 3'-0" | 7'-0" | 4'-0" | 5'-0" | 17 | 1-3/4 | 2-3/4|
+---------+--------+-------+--------+-------+-------+-------+-------+-------+
|8 | 750 | 3'-6" | 7'-6" | 4'-0" | 5'-0" | 19 | 2 | 3 |
+---------+--------+-------+--------+-------+-------+-------+-------+-------+
|10 | 900 | 3'-6" | 8'-6" | 4'-0" | 5'-0" | 21 | 2-1/4 | 3-1/4|
+---------+--------+-------+--------+-------+-------+-------+-------+-------+
|12 | 1100 | 4'-0" | 5'-6" | 4'-6" | 5'-6" | 24 | 2-1/4 | 3-1/2|
+---------+--------+-------+--------+-------+-------+-------+-------+-------+
|14 | 1200 | 4'-0" | 5'-0" | 4'-6" | 5'-6" | 25 | 2-1/2 | 3-3/4|
+---------+--------+-------+--------+-------+-------+-------+-------+-------+
|16 | 1500 | 4'-6" | 10'-0" | 4'-6" | 5'-6" | 28 | 2-3/4 | 4-1/4|
+---------+--------+-------+--------+-------+-------+-------+-------+-------+
Figure 4.--Single-chamber septic tank. Note alternate use of baffle
boards where sanitary tees are omitted at inlet and outlet.
The siphon provides intermittent discharge of effluent, which allows
time for the disposal area to rest and aerate between discharges. This
is more important where the discharge is nearly continuous than in
small installations.
The frequency and volume of the discharge into the tile field are
controlled by the sizes of the siphon and the dosage chamber. The
dealer should be informed of the size of the tank and the number of
persons in the household, in order that he may furnish the proper
unit. A 3- or 4-inch siphon will be adequate for almost any farmhouse
installation.
Construction
Most septic tanks are built of concrete cast in place, since in this
way there is a minimum possibility of cracks developing. Concrete
blocks, however (not cinder blocks), stone, brick, or structural tile
are sometimes used. Prefabricated commercial tanks of concrete and
various other materials also are available.
[Illustration]
+--------------------------------------------------------------+
| SIPHON |
+--------------------------+-----------------------------------+
|_Diameter of siphon |_Clearance under bell |
| A - 3" or 4"_ | E - 2"_ |
+--------------------------+-----------------------------------+
|_Diameter of bell |_Distance across U-trap |
| B - 10"or 12"_ | F - 10" or 12"_ |
+--------------------------+-----------------------------------+
|_Bottom of outlet |_Bottom of outlet |
| to discharge line | to bottom of U-trap |
| C - 20-1/2" to 25-3/4"_| G - 12" or 13"_ |
+--------------------------+-----------------------------------+
|_Drawing depth |_Height above floor |
| D - 13" to 17"_ | H - 7-1/4"to 11-3/4"_ |
+--------------------------+-----------------------------------+
| DIMENSIONS OF DOSING CHAMBER |
+-----------------+-------------------+------------+-----------+
| _Number of |_Depth below | | |
| persons served_ | discharge line_[3]| _Width_[4] | _Length_ |
+-----------------+-------------------+------------+-----------+
| 4 or less | 16-1/4" to 20-1/4"| 3'-0" | 6'-0" |
+-----------------+-------------------+------------+-----------+
| 6 | " | 3'-0" | 7'-0" |
+-----------------+-------------------+------------+-----------+
| 8 | " | 3'-6" | 7'-6" |
+-----------------+-------------------+------------+-----------+
| 10 | " | 3'-6" | 8'-6" |
+-----------------+-------------------+------------+-----------+
| 12 | " | 4'-0" | 8'-6" |
+-----------------+-------------------+------------+-----------+
| 14 | " | 4'-0" | 9'-0" |
+-----------------+-------------------+------------+-----------+
| 16 | " | 4'-6" | 10'-0" |
+-----------------+-------------------+------------+-----------+
[3] Depending upon depth C of siphon.
[4] Same as single chamber tank fig. 4.
Figure 5.--Typical design for a concrete septic tank with a dosing
chamber and a siphon.
Masonry units should be laid in full beds of 1:3 cement mortar and
the walls and floor plastered with at least a 1/2-inch coat of 1:2
mortar. Cells of concrete blocks and tile must be filled with concrete.
Masonry walls are generally 8 inches thick, and care must be taken to
follow _inside_ dimensions given for concrete tanks. Directions for
laying structural tile, brick, and concrete blocks can be obtained from
dealers or trade associations.
Commercial tanks are suitable if they embody the essential features
given in this bulletin. Capacities should be as recommended in figure
4 for concrete tanks. Proper installation and periodic servicing also
are essential. Tanks badly damaged in handling should not be used.
Rapid corrosion of steel tanks will result if the asphalt coating is
impaired. Minor defects in precast masonry tanks may often be overcome
by plastering the interior with cement mortar.
BUILDING A CONCRETE TANK[5]
[5] For information on making and placing concrete, see Farmers'
Bulletin 1772, Use of Concrete on the Farm.
A convenient method of assuring correct location of the tank is to
build a frame as shown in figure 6. Care is necessary to aline it with
the center line of the inlet and outlet and to level it so that the
distance from the bottom of the 2 by 4's on the form to the lower edge
of the inlet hole in the form will permit it to be set at the grade of
the house sewer. This frame is used to support the form for the tank.
To avoid caving the edges, drive the stakes supporting the frame before
beginning the excavation. The lumber in the frame can be used later to
make part of the tank baffles.
[Illustration: Figure 6.--Method of outlining a septic-tank excavation
on the ground surface.]
Figure 7 shows how an inside form can be built and hung in place. The
inlet and outlet tees should be carefully set and tied in place before
the concrete is poured. A single length of pipe should be joined to
the tee, so that the two can be set in the form as one unit. In most
cases the earth walls of the excavations will serve as the outside
forms unless the soil is sandy or gravelly and the excavation is deeper
than 5 feet. If outside forms are used, space must also be provided for
them. Forms should be constructed before the excavation is made and the
tank built as soon as practical, to avoid warping of forms and caving
of earth walls.
[Illustration: Figure 7.--Inside form hung in place for single-chamber
septic tank, also a form for casting concrete-slab cover in sections.]
County agricultural agents, local health departments, building-material
dealers, and other agencies often have forms that may be borrowed or
rented.
THE EFFLUENT SEWER
The effluent sewer should be constructed in similar manner and of the
same materials as the house sewer and on a slope of 1/8 inch to 1 foot.
This line, however, may be laid of terra-cotta pipe, as cast-iron is
not considered necessary except in unusual cases. This line should
always terminate in a distribution box from which the tile lines
of the disposal field lead away. For steep slopes the arrangement
shown in figure 9 (p. 15) is practical. Joints must be of root-tight
construction if the sewer is in the vicinity of trees or shrubs. The
length of the sewer depends upon the distance from the tank to a safe
site for the disposal field.
THE DISPOSAL FIELD
Correct installation of the disposal field is of great importance for
proper functioning of the septic tank. Therefore, the width, depth,
and spacing of the tile trenches must be carefully selected. Line of
4-inch, open- jointed, agricultural drain tile laid in shallow trenches
are ordinarily used. Perforated fiber drain pipes also may be used and
are obtainable in 4-foot lengths.
A distribution box with an inlet for the effluent sewer and an outlet
for each individual run of disposal tile is the best means of dividing
the flow. The outlet serving a large or double disposal field may be
alternately opened and closed by means of a sewage switch that permits
half the disposal field to work and rest alternately several weeks. A
switch is especially helpful in tight soils but should not be provided
unless proper maintenance is assured, so that a portion of the disposal
field will not be left to handle the entire load of the system for an
indefinite period. There are many variations of boxes, but figure 8
shows a practical type.
[Illustration: Figure 8.--Typical distribution box.]
Shallow Tile Lines
The disposal tile should not be more than 18 to 24 inches below the
surface, and where the ground-water level rises to the bottom of the
trench special underdrains, described on page 16, are necessary.
Special provisions must also be made where tight soils are encountered.
These methods are described in the section entitled "Disposal methods
in tight or wet soils."
The table in figure 9, together with the information given in table 1,
below, may be used for estimating the number of tiles needed in any
particular soil type. If there is any doubt about this requirement, a
percolation test should be made in the disposal field, as follows:
Dig a hole 1-foot square and to the depth at which the tile is to be
laid. This depth in most instances will be about 24 inches and should
not exceed 36 inches. Fill the hole with water to a depth of 6 inches
and observe the time required for the water to seep away; divide by 6
to get the average time for the water to fall 1 inch. The test should
be repeated at three or four different points in the disposal field
and the average time noted for all tests used. The data in table 1 can
then be used to determine the number of tiles needed. Where 1 hour is
required for the water to fall 1 inch the soil is totally unsuitable,
and another site should be selected. Soil conditions at the time of
the test may vary from year-round average conditions, and this factor
must be taken into account. If the soil appears exceptionally dry,
greater depths of water may be used or the test repeated in the same
hole. In no case should tests be made in filled or frozen ground. Where
fissured rock formations are encountered, advice should be sought from
sanitation specialists.
Table 1.--_Determining tile-disposal field requirements from
percolation tests_[6]
------------+----------------------++------------+---------------------
Minutes | Effective absorption|| Minutes | Effective absorption
required | area required, per || required | area required, per
for water to| person, in bottom ||for water to| person, in bottom
fall 1 inch | of disposal trenches ||fall 1 inch | of disposal trenches
------------+----------------------++------------+---------------------
| _Square feet_ || | _Square feet_
| || |
2 or less | 26 || 10 | 52
| 30 || 15 | 63
| 36 || 30 | 90
| 40 || 60[7] | 120
------------+----------------------++------------+---------------------
[6] A minimum of 150 square feet should be provided, equal to 100 feet
of 18-inch trench.
[7] If more than 60 minutes, use special design with seepage pits or
sand-filter trenches.
Figure 9 suggests methods of arranging the tiles in disposal fields
under varying conditions and the length of tiles needed.
[Illustration: Figure 9.--Arrangements for tile-disposal fields, method
of laying tile, and length of tiles needed.]
SIZE AND MINIMUM SPACING REQUIREMENTS
FOR DISPOSAL TRENCHES
+---------+----------+----------------------+-------------+
| TRENCH | TRENCH | EFFECTIVE ABSORPTION | TILE LINES |
| WIDTH-W | DEPTH-D | AREA IN SQUARE FEET | SPACING-S |
|IN INCHES| IN INCHES| PER LINEAL FOOT | IN FEET |
+---------+----------+----------------------+-------------+
| 18 | 18 to 30 | 1.5 | 6.0 |
| 24 | 18 to 30 | 2.0 | 6.0 |
| 30 | 18 to 36 | 2.5 | 7.5 |
| 36 | 24 to 36 | 3.0 | 9.0 |
+---------+----------+----------------------+-------------+
Wider spacing of the lines desirable where available area permits
DISPOSAL-TILE TRENCH
Disposal-tile lines--Maximum length for each line 100 feet.
All lines to be equal in length.
Disposal-tile lines to slope 2" to 4" per 100 feet, not over 6".
Sewer-tile lines to slope 1/8" to 1/4" per foot.
DISPOSAL METHODS IN TIGHT OR WET SOILS
If the soil is heavy clay or has tight formation, yet shows some
porosity from percolation tests, the efficiency of the field may be
increased by placing below the tile lines 12 to 15 inches of additional
filter material (washed gravel, crushed stone, slag, clean cinders, or
clean bank-run gravel 3/4 to 2-1/2 inches in size). When the surface
soil is tight and is underlain by porous soil, sufficient drainage
is sometimes obtained for the smaller installations by omitting the
tile field and providing a dry well at the end of the effluent sewer,
provided the water table will not be contaminated. Larger systems under
such soil conditions should have a tile field, and absorption can be
increased by boring 6- or 8-inch holes down to the porous stratum and
filling them with gravel or sand; the holes should be 4 to 6 feet
apart. Another and perhaps the best practice is to excavate the tile
trenches 4 to 6 feet and install a lower tile line, as shown in figure
10. This latter method is especially desirable if the upper tight
stratum is especially thick, or if there is no porous lower stratum, or
if in irrigated regions and where the disposal field is limited in area.
Where the underdrain tile is not used, the absorption capacity of the
field can be increased by providing a rock-filled trench across the
lower end of the tiles for the full width of the field. The depth
should be not less than 5 feet and the width not less than 3 feet.
On account of the beneficial action of bacteria in the upper soil
layers it is highly desirable to confine the effluent near the surface
rather than to use underdrains. Purification becomes slower and less
effective, the deeper the drains.
In situations where the soil contains considerable moisture or is even
saturated, the field may be improved by partially encircling it with a
tile line laid to serve as a drain. Such a line should be on the high
side and have surface outlets for removing the water from the soil. It
should not be laid so close to a disposal tile line that it will drain
the sewage effluent from the disposal field onto the surface of the
ground.
[Illustration: Slope of disposal tile 2 to 4 inches per 100 feet. Slope
of underdrain tile not less than above.
Plug upper end of underdrain tile lines, lower end to discharge into
rock-filled seepage pit or into other approved outlet.
Figure 10.--Filter trench with underdrains.]
When the tile field is underlain by stratified rock or where
under-drainage is necessary, advice should be sought from the public
health authorities, as regulations in some States may not permit the
use of certain methods.
CARE AND MAINTENANCE OF SEPTIC TANKS
A septic tank when first used does not need starters, such as yeast,
to promote bacterial action. A good septic tank normally requires no
maintenance other than a yearly inspection and an occasional cleaning.
Frequency of cleaning depends on the capacity of the tank and the
quantity and composition of the sewage. Tanks of the size recommended
in this bulletin may require cleaning at intervals of 3 to 5 years.
The tank should be cleaned when 18 to 20 inches of sludge and scum has
accumulated. If a drain has not been provided, sludge may be removed by
bailing or by pumping with a sludge or bilge pump. It is not necessary
to remove the entire liquid contents. Burial in a shallow pit or trench
with at least 18 to 24 inches of earth cover at a point remote from
water sources is the most practical method for disposing of these
wastes.
A septic tank is intended to handle sewage only. Coffee grounds and
ground garbage may be included if there is an ample supply of water for
flushing and the tank is cleaned more frequently than would otherwise
be done. The size of the tank should be increased at least 25 percent
if these materials are included in the sewage.
=_Do not use matches or an open flame to inspect a septic tank, as
the gasses produced by decomposing sewage may explode and cause
serious injury._=
EFFECT OF DRAIN SOLVENTS AND OTHER MATERIALS
Soap, drain solvents, and other mild cleaning or disinfecting solutions
used for normal household purposes cause no trouble in the tank.
Constant use in large quantities, however, and disinfected wastes from
the sickroom may prove harmful.
Wastes from milk rooms, strong chemicals used in sterilizing equipment
or in photographic work, and the wastes from filters or water softeners
not only reduce bacterial action but also cause abnormally rapid
accumulations of sludge and clogging of the tile lines.
PROTECTION AGAINST FREEZING
Septic-tank systems seldom freeze when in constant use. Warm water
and the decomposition of the sewage usually maintain above-freezing
temperatures. In cold regions there is trouble from freezing if various
parts of the system are not covered adequately. If the system is to be
out of service for a period of time or if exposure is severe, it may be
advisable to mound over the poorly protected parts of the system with
earth, hay, straw, brush, leaves, manure, snow, or the like.
In cold regions it is not advisable to install the entire system below
frost depth, as this will remove the effluent from the action of the
aerobic bacteria in the upper layers of the soil and make the system
generally less accessible.
New systems put into operation during very cold weather may freeze
unless large quantities of hot water are discharged during the first
few weeks.
SEPTIC-TANK TROUBLES
In sewage disposal, clogging of the disposal field is the most common
trouble. This may be caused (1) by a tank too small for the volume of
sewage, (2) by failure to clean the tank regularly, (3) by interior
arrangement that does not provide slow flow through the tank or that
allows scum or sludge to pass out with the effluent, or (4) by a
disposal field that is too small or is incorrectly built.
The remedy for a clogged disposal field is to dig up and clean the
tiles and re-lay them 3 or 4 feet to one side or the other of their
former position. Sometimes a tile line can be cleaned by opening up
the line at each end and flushing it thoroughly with a hose. With this
method provision must be made to drain off and safely dispose of the
water used for flushing.
Tile lines laid with improper slope allow the effluent to collect in a
limited area and saturate the soil, causing odors. Bacteria cannot work
in such areas, where the soil becomes sour, or "sewage-sick." These
lines must be relaid on the correct slope. Odors or a water-logged soil
may also indicate that the disposal field is too small.
House sewers frequently clog. This is due, in most cases, to roots
and less frequently to trash, garbage, or other foreign materials
discharged with the sewage. Greases in the sewer may cause trouble,
especially when the slope is insufficient to give the sewage a
cleansing velocity. Drain solvents will sometimes remove the
obstruction, but more often it is necessary to clean the sewer by
rodding. In some cases it may be necessary to dig up the line to reach
the obstruction or, at least, to open the line so that it can be rodded
from two directions. When it has been cleaned, a manhole could be built
for use in case of future trouble. If stoppage is due to roots it may
be necessary to re-lay the sewer with root-tight joints, or to move
either the sewer or the vegetation so that roots cannot reach the line.
GREASE TRAPS
Grease traps (fig. 11) are not recommended for the average farm,
because they clog easily and require frequent cleaning, but they are
desirable for boarding houses and tourist camps where large quantities
of grease are produced. The septic tank if of proper design and size
will take care of the normal grease from most farm kitchens.
The traps must be several times larger than the quantity of greasy
water discharged into them at any one time, in order to allow the
greases to rise, but they should not be of less than 30 gallons'
capacity.
The trap is best located in an accessible place in the basement or
under the house close to the source of grease and safe from frost.
Outdoor locations at shallow depths require a covering for insulation
against freezing. Grease traps should be connected to the kitchen sink
only and not to laundry, shower, or water-closet wastes. They must be
cleaned periodically for satisfactory operation, and the outlet should
be properly trapped.
[Illustration: Figure 11.--Typical grease trap.]
DISPOSAL OF DRAINAGE FROM FIXTURES OTHER THAN TOILETS
When the farmhouse does not have an indoor toilet but does have a
kitchen sink or other similar fixtures, the drainage can be disposed
of as shown in figure 12. Even where septic tanks have been installed,
it is sometimes advisable to have a second disposal field for other
fixtures than the toilet, to avoid overloading the tank, especially
where large quantities of laundry water are discharged at one time.
[Illustration: Figure 12.--Disposal of drainage from kitchen fixtures,
using a line of terra cotta or fiber drain tile surrounded with
gravel. One or two rock-filled pits at the end of the line increase
the absorption area and are desirable where there are several fixtures
or the soil is nonporous. The pits may be lined with boards or masonry
laid without mortar and provided with a tight cover.]
These wastes are not likely to create serious health hazards, but they
become nuisances if discharged promiscuously on the ground surface.
Such drainage should never be permitted on the watershed of a spring.
Coarse sand and gravel, 12 to 18 inches deep, may be placed on the
bottom of the pit, to strain out small particles of solids, which might
clog the pores of the soil. If, after a few years, the sand or gravel
becomes clogged with solids, it should be replaced with clean materials.
If excessive quantities of grease are permitted to enter the sink
drain, a grease trap may be advisable.
CESSPOOLS
Cesspools are cheap in first cost but high in maintenance costs and
often become nuisances. They should be located at least 150 feet
from wells, 15 feet from seepage pits and property lines, and 20 feet
from dwelling foundations. They should never be used in the vicinity
of shallow wells and, in any case, only where permitted by State
regulations.
The cesspool depends for its action upon seepage into the surrounding
soil and consequently is particularly unsatisfactory in tight clay
soils. In more open sand and gravel soils the seepage is reduced as
the pores of the soil become clogged with particles of solids, until
it stops entirely, and overflowing occurs. Emptying and then cleaning
the walls and floor of a cesspool do not fully open up the clogged soil
pores, and overflowing can be expected to occur soon again.
Solids in cesspools must be removed from time to time by bailing or
pumping and should then be buried 18 to 24 inches deep in a trench
where the water supply will not be endangered. Caustic potash (lye)
will to some extent liquefy solids in a cesspool. This treatment does
not eliminate the necessity of removing the contents when periodic
inspection shows that the cesspool is nearly full. Caustic potash
converts the greases into soft soap, whereas caustic soda forms a hard
soap that does not readily dissolve. The chemical treatment is not
effective in liquefying solids in the pores of the soil surrounding the
cesspool.
[Illustration: Figure 13.--A neat, whitewashed lattice along the paved
walkway provides protection from cold wind and rain and gives added
privacy.]
When clogging continues and cannot be corrected, in most cases the best
solution to the problem would be to abandon the cesspool and install
a septic-tank system with tile disposal field. The cesspool should be
completely filled with stones, earth, or other solid materials to avoid
possible cave-ins.[8]
[8] See The Septic Tank, p. 8.
PRIVIES
A privy when safely located and properly built and maintained is
satisfactory for its purpose on the farm. Privies should be built 50
to 150 feet from the farmhouse, preferably on the opposite side of the
house from prevailing winds, and at least 50 feet from the well. A site
downhill from the well is generally safest. In some cases, however,
the ground water may flow in a direction opposite to the slope of the
surface, in which case the privy should be built on the other side of
the well. Direction of flow may sometimes be learned from soil surveys,
well-driller's data, or other similar sources. A distance of at least 6
feet from fences or other buildings allows for proper mounding of the
privy and keeps it away from roof drainage from adjacent buildings.
Good, tight construction with screened ventilators keeps insects and
birds from entering, prevents rapid deterioration of the building, and
provides greater comfort for the user.
Certain features, while not essential to sanitation and satisfactory
service, add to personal convenience. A paved walkway, well protected
from cold winds and rain, is desirable. A neat, whitewashed lattice, as
shown in figure 13, an arbor covered with vines, or a hedge screen adds
to privacy.
The earth-pit privy is the simplest to build and the one most widely
used. It is not generally recommended in localities where underground
rock has crevices.
For a sanitary type of privy with reinforced concrete[9] floor, riser,
and supporting sills see figure 14. Because privy units are commonly
used as urinals, the use of impervious materials for risers and
floors facilitates cleanliness. In the colder climates, wood treated
with a preservative is durable and reduces the problem of moisture
condensation. Therefore, wood could be used if approved by the State
department of health.
[9] For information on making concrete see Farmers' Bulletin 1772, Use
of Concrete on the Farm.
When it is considered impracticable to build the slab and riser
of concrete, these parts may be of wood, as shown in figure 16.
The building itself may be as shown in either illustration. A wood
structure is easy to move to a new location.
A pit with a minimum capacity of 50 cubic feet[10] will usually serve
five people over a period of 5 to 10 years. The privy should be moved
when the pit is filled to within 18 or 20 inches of the top and a
strong disinfectant spread in the old pit before covering it with earth.
[10] Recommended by the Committee on Promotion of Rural Sanitation,
Public Health Engineering Section of the American Public Health
Association, 1932.
[Illustration: Figure 14.--Sanitary type of privy. Detailed plans and
a bill of materials for this design can be had from the United States
Public Health Service, Washington 25, D. C.]
It is important to have the earth-pit privy more than 50 feet from the
well even where the water table is not near the surface. The ground
water should flow from the well toward the privy, and it is important
that this direction of flow be determined in advance.
Wood is most commonly employed for the main part of the building. The
ground outside should be sloped as shown, to shed water away from the
building, and the roof should extend beyond the walls to shed water
away from the pit.
CARE AND MAINTENANCE
All privies require periodic attention. Seats and covers should be
washed weekly with soap and water or with disinfectants, such as
cresol, pine oil, and hypochlorite or chloride of lime. These have
deodorant properties and are available at most grocery or drug stores.
Druggists generally carry a more refined product and consequently the
price is higher.
During the fly season fly and mosquito eggs will be destroyed by
pouring half a pint of crude oil, crankcase oil, fuel oil, kerosene, or
borax solution (1 pound powdered borax dissolved in about 10 gallons of
water) over the contents of the pit about once a week.
[Illustration: Figure 15.--Pit privy of all-wood construction. The
sills and riser of this type should either be treated or made of
cypress, redwood, cedar, locust, fir, or other decay-resistant wood.]
Odors from privy pits and vaults can be reduced by covering the
contents with dry earth, ashes, manure, or sawdust. These materials
fill up the pit rather quickly, but can be used where other deodorants
are not available. Sometimes two cakes of yeast dissolved in 2 gallons
of water are effective in reducing odors. Commercial deodorants are
available from suppliers of disinfectants.
If a person in the family has typhoid fever or is a carrier of that
disease or has dysentery, it is advisable to disinfect the excreta.
Fire, live steam, boiling water, and such chemicals as caustic
soda (sodium hydroxide), caustic potash (potassium hydroxide), or
hypochlorite or chloride of lime may be used. The heat generated by the
slacking of quicklime is also effective. Best results are obtained if
the infected material is treated prior to depositing it in the privy.
Further advice may be obtained from physicians, local health officers,
or State health departments.
CHEMICAL CLOSETS
In general, chemical closets should be used only where there are
elderly or infirm people unable to get outdoors, particularly in
winter-time. In some localities their use is forbidden by law because
of improper maintenance. Strict adherence to the manufacturer's
directions for making the installation is necessary to obtain
satisfactory service. The chief advantage of chemical closets is that
they may be within or adjoining the house and used without regard
to soil or ground-water conditions. The caustic chemicals required,
if used properly, reduce the quantity of solid matter by liquefying
action, disinfect and deodorize the contents, and lessen danger from
flies. Disadvantages are the cost of the chemicals and necessity for
careful and constant maintenance.
The chemical-tank closet is generally recommended rather than the
dry-type chemical closet. Three variations of tanks are available
commercially. One type contains a clean-out opening in the top of the
tank, through which the contents are removed by pumping or bailing.
The second type has, in addition to a clean-out opening, a drain valve
at the bottom, which is operated by a handle extending to a clean-out
opening, so that gravity drainage of the tank is possible. The third
type is self-draining; as the excreta are added an equal volume of
liquid is spilled out the overflow. The solid matter must be removed
manually or through the sludge drain.
The last-mentioned type requires frequent addition of chemicals, and
the others are recharged after each emptying. The presence of odor is
an indication of insufficient chemical or of the need for emptying
and recharging. The same precautions apply to selecting an area for
disposing of the tank wastes as to disposing of the materials removed
from cesspools.[11] Since the contents of chemical closets are caustic,
they may kill vegetation with which they come in contact.
[11] For disposal methods in tight soils, see p. 16.
The dry-type chemical closet is cheap, simple, and easy to install
but requires frequent emptying. Pine tar and coal tar will accomplish
only partial disinfection and deodorization, but caustic disinfectants
produce liquefication in addition if used in sufficient quantities.
The caustic chemicals may cause burns if the receptacle is too full or
if spilled where they come in contact with the body.
This form of closet is more of an expedient than a permanent
installation, and daily care is necessary to prevent the development of
insanitary conditions.
DISPOSAL OF GARBAGE AND TRASH
Domestic garbage and trash on farms can be divided into four
classes--(1) waste of plant or animal origin suitable for animal feed,
(2) unpalatable plant or animal waste, (3) combustible trash, and (4)
noncombustible material. The disposal of these wastes is simplified if
the four classes are kept separate.
Trash to be burned should be kept dry. Coffee grounds, tea leaves,
citrus rinds, fish heads, entrails, eggshells, and similar material are
most readily handled if drained and put in paper sacks.
Cans should be placed where they will not collect water and become
breeding places for mosquitoes. Cans will corrode faster if heated
sufficiently to burn off all grease. When the trash accumulates it
should be hauled to some out-of-the-way place, such as a gully, or
buried.
Neat-appearing garbage containers are desirable for kitchen use and
should be small enough to require daily emptying. Large containers
may be placed within easy reach outside the house and screened with a
lattice fence or shrubbery. Substantial containers of rust-resistant
metal will not quickly become an eyesore and a nuisance. Tight covers
should be used to keep out prowling animals and to eliminate the habit
of tossing wastes from the back door. Open or wooden containers are not
recommended.
A good way to protect the garbage pail is to place it in a small pit
that has a manhole frame and a lid that can be raised by foot pedal. A
gravel bottom in the pit will assist in draining water away.
Outdoor receptacles, if emptied and cleaned once a week, generally do
not become foul. Grease, coffee grounds, and other similar materials
that adhere to the sides of containers can be removed by scraping with
a little sand prior to scalding.
Electrically operated units grind garbage and bones and discharge the
material through the kitchen-sink drain. They will not handle tin cans,
glass, and the like. They may be used on farms if the septic tank is
larger than normal and if sufficient water is available for flushing
the drain to prevent clogging.
Garbage to be fed to animals should be preserved as carefully as is
human food. To prevent the spread of trichinosis and other diseases, it
should be cooked before it is fed to hogs. Garbage left uneaten by the
animals should be disposed of by one of the methods described above.
Incineration is the most sanitary method of disposing of farm wastes.
Garbage, however, is not easily burned. Figure 16 shows a type of
incinerator[12] suitable for farm homes. Details of construction for
a brick incinerator are given in figure 17. Brick, stone, concrete,
or other fire-resistant material may be used. Commercial incinerators,
some of which are designed to be built into the house, also are
available, although these cost considerably more than the home-made
type shown.
[12] Blueprints of this design may be obtained from the extension
agricultural engineers at most of the State colleges.
A limited quantity of refuse may be burned in a kitchen range or a
furnace, but it may cause accumulations of grease in the flue and
require frequent cleaning to prevent fire.
Next to burning, burial is the most desirable method of waste disposal.
Waste material may be deposited in a trench 3 or 4 feet wide, 7 or 8
feet long, and 4 or 5 feet deep and covered with earth when filled to
within 18 inches of the top. If there is no fire hazard, the contents
of the trench may be burned.
Garbage may be included in a compost heap with leaves, peat, manure,
and similar materials. The compost pile should be in an inconspicuous
place, built up to the desired height with materials that will rot,
and then covered with 2 or 3 inches of earth. The top should be
level and the sides steep sloping. It is necessary that the material
being composted be kept moist; otherwise it will not rot. Frequently
commercial fertilizer is added to increase the fertilizing value of the
compost.
Ashes and clinkers removed from furnaces should be placed in metal
containers to eliminate fire hazard. Wood ashes may be spread on the
lawn or garden, as they have some fertilizing value.
[Illustration: Figure 16.--A satisfactory incinerator for household
use.]
[Illustration: Figure 17.--Details of construction of the household
incinerator pictured in figure 16.]
Trash burners of various designs suitable for burning small quantities
of paper and rags are available or may be improvised. The main
requirements are provision for adequate draft and for preventing the
escape of burning paper or live embers.
U. S. GOVERNMENT PRINTING OFFICE: 1948
For sale by the Superintendent of Documents, U. S. Government Printing
Office Washington 25. D. C. -- Price 10 cents
* * * * *
Transcriber Note
Illustrations were repositioned so as to not split paragraphs.
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