xt7n2z12q28g https://exploreuk.uky.edu/dips/xt7n2z12q28g/data/mets.xml   Kentucky Agricultural Experiment Station. 1931 journals kaes_circulars_001_2_131_02 English Lexington : The Service, 1913-1958. Contact the Special Collections Research Center for information regarding rights and use of this collection. Kentucky Agricultural Experiment Station Circular (Kentucky Agricultural Experiment Station) n. 131 text Circular (Kentucky Agricultural Experiment Station) n. 131 1931 2014 true xt7n2z12q28g section xt7n2z12q28g r .  UNIVERSITY OF KENTUCKY
i COLLEGE OF AGRICULTURE
und ‘· 
  Extension Division
""“‘ ’ THOMAS P. coopea, Dean and Director
 ; CIRCULAR NO. 131
 ° (REVISED) .
vi, iv 
il>l».·s.  -
 Y Septic Tanks for Sewage Disposal
~ Lexlngton, Ky.
ij  June, 1931
Published in connection with the agricultural extension work carried
on by cooperation of the College of Agriculture, University of Kentucky,
with the U. S. Depnrtnient of Agriculture, and distributed in furtherstnce
_ 0f the work provided for in the Act of Congress of May S, 1914.
* .

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   {
CIRCULAR NO. 131
Q (REVISED)
~ Septic Tanks for Sewage Disposal
By EARL G. WELCH and JAMES B. KELLEY*
 · THE NEED FOR SAFE DISPOSAL OF SEWAGE
Q l11 Will) the .I)llllIl(' St‘I`\'l*'C Laboratories at the Kentucky
1 i\!l'l<‘lIlllll'&lI I‘iX]N’l'IIII<'Ill Station analyzed (5.4lO samples of
T \\`2Ill‘I' t`1·11111 \'ilI·IIIll¥ parts ot` the State, (lf these. 46.5 pereent
I <‘¤\Ill2llll•‘\\'1\I`{l l\T:1Iso11,
_ \

 I iii]
4 Kentucky Extension Circular N0. 131 ’ 
of hu1nan exerement is the cause of contamination in many of ‘i 
these wells and springs. *
‘ It is well for anyone planning a sanitary sewage disposal i
system to keep the following principles in mind: *
1. The system should be so located that drainage either I
above or below ground toward a nearby well, cistern or spring  »
is practically impossible. ‘
2. The final disposal should be made in the upper 18 i
inches of soil where sunlight, air and soil bacteria may accom- .
plish purification.
3. Body excremcnt should never be permitted to drain ~
or be washed into a small stream, sinkhole or tile drainage  ~
system. *
4. Outside toilets should lie so constructed and screened {
that annuals or flies cannot in any way come in contact with .
sewage held in the vault.  »
TYPES OF DISPOSAL SYSTEMS FOR VARIOUS CONDITIONS  
1. Jlodcra Plumlifng in. the Home. Houses supplied with  
running water and modern plumbing should be provided with  v_
K a septie tank. A septic tank is considered the niost satisfactory
means of residence sewage disposal as it is water-tight, and the ’
overflow is disposed of in the soil where soil bacteria, air and .
A sunlight purify it.  _
Frequently cesspools or dry wells are used for the disposal  .
of sewage from houses with running water. As a rule these are  ,
condemned by sanitary engineers. The operation of the cess-
pool depends on the seepage of the liquefied sewage thru the p
porous walls of the underground tank into the adjoining soil »
area. In this method of sewage disposal seepage is at a depth  t
of several feet below the surface of the ground where there is y
little chance of purification by air, sunlight or bacteria in the I
soil. The sewage may filter into a water supply, which is the  
greatest objection to the cesspool. It the liquid docs not seep
thru the walls, the cesspool soon fills to overflowing and beeomeS _
a nuisance. A cesspool that is a menace to water supplies should t
not he tolerated.

  
 1 S('[l[l»(J T1111/as fur S1*w11gc Disposal 5
of ` Z2. I\’l.[l']1()11 Nin/1* 11111] I'll1Il[}. 111 l'Tl21l1_Y rural houses only
 `· 11 1{111'1l1'11 s1n1< i1l111 111111111 21l'1‘ ]>1‘11\'i111·<1. 111 such 111111ses u $(511111;
1Sa1 A 111111- 111111* 111- l1N1‘<1 111 2|11\'2i111iiQi‘. '1`1l(‘ \\'21S11f \\'EI1('l‘ from 1111;
1 h1111{ 111111* 111- 111'&11111‘11 111111 1111- $1*11111* 1I1'1\'_\` 211111 111115 s111111ly 1111:
11111- { \\`;|11‘l' 1·ss1-1111111 111 1111- 111|111‘1·111'l1<111 111' 1111* s111i11s 111 1111; S(’\\`Z1g13,
ing Q '1‘111· s1·111i1· 111*11*5* 111:11* 111- 1`111111;!1`(1 111 21 s1-111i1· 1}11l1{ i1' 1111- 1l()1lS('
11111-1* is 111*11vi11•·11 \\`111l 11111111·1*11 1111111111i11g_
18 1 JL _\‘lI 1•)1IIl)l1)1[/ “'1l’iI', '1`111 S21ll1l211'}' 111111*1 with (‘()111‘1'1'1(’
10m` 1 \'i11l11 111111 11*1-11 N1'1'1'1‘111'11 :11111 \'i‘111l1211•‘11 111111-1 111111$(’ is 1111- 11es1
1l11‘&111> 111` l11S1)1I>111;! 111. \\`21S11‘ 1.1"1111 1111- 111111121ll 11(l11)` 11*111-11 1*1111-
min ning \\'2ll1*1' is 11111 21\`2l11&11)11*.
nagc 1
 i THE SEPTIC TANK AND DISPOSAL SYSTEM
  L T/11 ,11*111111 111 11 N111/11* T11n].‘_ -\ >1*11111: 121l11{ 1s il \\`211C1‘·
 _ 11g111111111;i11w11i1·11s1-wuu·1- is 111-111 1111111 thc s111i11s 11(*1'(_1111C
 1 111111··1i1·11 11)* 1111- 111·ti1111 111` 1111111.1i()111(' 11111'1(*1·111*. A su11111 c11111-
NS · 1)l1>l‘11 111` s1»li11s 111 1111- Sl‘\\`i1Q1‘ 1.111'l11S 1111 11111 1111111(1 111 1110 1211l1{. *
with 1 i1`111S·S1‘111l1 1111s11·111·1s 111(`· ;11·1·1-ss 111` :111* 111 1111- 1111111(1, 111115 p1`O\`111—
with   11111 1111.111 \\`111`1{1111.{’ 1·‘<11111l11-1111S.1i1l1‘ 1111- 1111:11-1*1111111 11u1·101‘1u. As 21
Otmw 1 1·1·s1111 111 1111- 112l1‘l1‘1`1111 111*111111 111 111l` 1111111. aus. 111111111 111111 sludge
d the 1 11111111‘1`1111.11111 1111111-111*111 211'1‘· 1»(11'1111.(1. '1`11(` s11111g1- s1-1111-s 111 1110
i and I 111>l11111·1-111 1111- 1:1111;, '1`111* 1111111*1 1111\\'S 1`1*11111 1110 121111; 1111*11 1111*
· 11u*111—_11111111-11 s1-11-1-1* 1111- 111 11111 11i$1111Ni11 111*1-u \\`111‘l`C 11 is 111s11*1·
1 111111-11 111 11111 s11i1 11;* 1l11‘&111S 111` 1·111111111111 l1l'§l'11‘1111l11‘111 11l'11111 111c
*110*11 111111 11111-11 _11>1111S, '1`111- 111111111 11s 11 111111111s 11*11111 21 s1111111· 1&1111{ 11121}`
EC MC 111- 1-11-:11* 11111 i1 is 1`2ll' 1l1'(1111 11111*1- 111111 1l\1lN1 111- ('111`1`1(\l`1 111111 1111-
CCS} . 11111 s11i1 l.111` 1111u1 1)1ll’1111‘21l1(111_ '1`111- :11*11:1 111211 is 111 1`l‘(‘1‘1\`(‘ 1111S
“ 1110  _ 111111111 1111151 111- \\'1*11 111-111111-11_ (*11111*1- ]l211111'E111}' 111· u1*1i111·1u11y. 11*
K $011  * 1111* s1111 \\`1111‘11 is 111 1`1‘('l‘1\'(‘ 1111- S(‘\\`21Q`1‘ 1s 11111 111‘1111111*1y 111*z1111011
dept}; V 1111-1-x1·1-ss 111` 111111s1111*1- 11111-11s 11111 1111- ;111* :11111 11111 211*1*111111‘ 1121Q1Cl‘111
101.0 1* _ \\'1111*11 21l‘1'11l1l1111S11 1111211 11111*i111·;1111111 1121111101 11\`1‘ 111111 \\‘01'1< Dl`0}1- '
111 the 1-1*11*. 11 11111 s11i1 is 11;*111* 111111 11111 11*1-11 (11`2l1111‘11. s11111·1u1 ])1`O\'1$1011
1S 11111  ` 1111151 111- 11111111- {111- (1181].111111111g 1111- S(‘\\`211IC‘, us S110\\`11 111 11g*111`9
t SCOP , 6- 1111* N1‘\\'21{,l`1‘ 11111s1* 1111 u111111111111 211111 1*1111111\*011 fl‘Oll1 1110 1?1111{
"`°‘“°‘  ·   ,, 1   - . . . ,
S1-011111 A gg?-*11%.-¥¤·¤-·`·2`-1}"l?J—` 11111 1`1`111-"`I-£ZY1`C.T11?}i`." ‘¥1—1€}·"`1.1l`1‘1‘1X.€"}JI~2i `31§1L`.‘l1"1D§"§§{`.‘{·..1ll??
` u:`;";;;1*M_H1l111*.   1111*11*1- 11*111-1*1· 111111- 111* 111- i111‘ is 111*1-s1-111, :11*11 1·1:1ss1111
1 1

 t  · 
6 Iicnttteky EJ;!cusz`un Circular N0. 131  {
without disturbing the scum which nortnally forms on top ot `
the water. lf water laden with any considerable amount of i
solid matter is permitted to enter tho tile lines of the distribu- V
tion system, the tile lines will soon become clogged aml a nuisance  .
will be created. i
Usually septic t2lI1kS are classitied as single-chamber or  I
double-chamber tanks. A siuglc-eltatuber tank is ono that has E.
only one compartment, altho the: cotupartment may contain one  
or more balfles. lu the single-chatnber tank, the liqueticd sow- ‘
age runs directly from the single compartment or liquefying  
chamber to the disposal line. A doulile-ehatuber tank has in  t
addition to the liquefying chatnber a second compartment called ig
a dosing chamber. The dosing ehamber eontaius an automatic ;
siphon which completely empties it when it becomes iilled with  
the overflow from the liquefying chatnber. 'l`his eoustt·ut·tion I-
permits sewage to enter the disposal beds two or three times a
day. The double-chamber tank is reconunended when the  i
amount of space for the disposal line is limited or when it is  
necessary to allow some time to lapse between doses of sewage to  =
A prevent the soil from becoming water-logged. `
For most conditions in Kentucky a single-chatnber tank is  p
recommended because of its simplicity and smaller cost. Single- Q 
. chamber tanks vary somewhat in construction but the essential  V
requirements are the same. Aside from the proper capacity.  »
the important features are au elbow to direct the entering sew-  `
age downward, under the seum, an arrangement to permit the -
liquefied sewage to flow frotu the tattk withottt carrying solitb
V into the disposal line and a fortn of battle to keep the incoming
sewage from disturbing the scum on top of the liquid in the  »
tank. In the plan recommended in this circular the T’s at the
inlet and outlet serve as baffles as well as means of direetinyz
the sewage at the inlet and outlet openings. The gas formed
by the bacterial action enters the soil thru the upper opening in _
the T at the outlet. The gas can not enter the sewer from the l
house because of the plug in the upper opening of the inlet T. p

  I Septic Tanks for Sewage Disposal 7
of i THE SEPTIC TANK INSTALLATION
ot
bu- V
mw  i I "X {ii `\
» I ( I I
\ 1 my / ‘ I
r GRAD Pi I ‘ 1 .
UI.  · llmygcwl T, L_ / ( I wurua DRAIN ]'lLE
<;I;1·II;rfr§>J0I y [I I I' TOTAL LE TH 99-{:0 PER _ _
has . (__ I I ,p;1z5or+, L 4-6 PEE \0O·0
one j   nous;  71 EPTIC T It ( I [
  .·   opus; TQ P   IL I, . /1
**“' _ . . I ,•/ 3/ E
.· I
)1llg S , I! I °
s in T // /’ / ‘·
I
anti 1; / It
natie 1 ’ I
with  Z_
I'llI*Il 1
ies a 4
the  i `
it is  { Fig. 1. A septic tank sewsige disposzil system.
gf} to  I
‘ The septic ttlllli sewage disposal system for farm houses
I _ _ shown in figure 1 eonsists of (1) a line of sewer tile to carry
l\ ` lS J . ‘
_ `I  ’ sewage from the house to the septic tank; (2) a grease trap
In! I‘- J  . . . , .
`t. l [ to remove excessive quantities of grease irom the water dra1n·
[lll l'l  ‘ . . . . _ . . .
_t( 1 mg trom the kitehen sink; (3) the septic tank where the solids
·1*1 v,  I . . , - · .
A ‘ . 111 the sewage a1·e liquefied; and (4) a disposal system wh1eI1
r sew- - . . .
{ may consist of a sewer l111e to earrv the lituefied sewaL*e to the
lt llI¤‘ ’ ` I `
_ disposal hue and tl1c dis Iosal li11e COIII wosed of aerieultural drain
LA¤¤l A
IO f
1   
A PLAN 1
1 T 1*1  *   =1 11  1
.—z>- .1 ¤ b'
Q L1  2*2 CQO55 ;,‘• l 1 j
1 1 .·.; ?.1 l 1  V
 . PLUG _ ·· ·"·4   1 —
if ;LL;.3L;é;,:. =1 1  1 Q1 1 .
. ·..€ *“““?··;"  ··. $-*1 _
19 1*5. ‘,‘?-, I 1 1 1
-1 `éi ··=·_ I I
N *1:1 Q'.; 1 1 1 ·
  =·.a 1 I 1 1  .
me 5 1 | 1 1 1.
¤{`° yr if 1 L··1 1 1
Z¥Z%_..,,._. . . ,. f` 6 `QJ; L _____. -1 f
’{·.¤ 1.*: S· ¤ ·'5' if  .`?I4’.“•‘2"·.’?.’. 52*.2 2. ‘
SECTION END V\LW  n
Fig. 2. A 1:1*0:1se 112111 :1:~: s1111w11 :11111ve is 113*1*11 1N'1\\'•J(*l\ kit0h011 sink ' 
IUN1 :€c\\'<·1` 1.0 p1’u\'1¤I11 uX1·¤·SS1\'1: :1I11111lI1\:4 111 L€1`1·21,S1· 1`1"1111 cl\1111`1|11.( 1110 S1·p1l1‘
tank.
Gfcrlsc Trap. T11e grease 11·:1p usually is 111:10011 just 0111·  
side 1110 1111011011 where it 0:111 110 CX2ll1l1l10(1 easily :11111 1110 g1·0:1s0 .
I removed when 11000ss:11·y, Tl1e 111*:1111 fl'0°1H the sink 0111111icS .

 Scpliu Tanks for Sewage Disposal 9
i directly lllt() the trap a11d the ovcrilow front tl1e trap enters the
lh" 5t‘\\`t‘l' lll1l‘ leading to the septic tank. 'l`he purpose of the grease
lll°‘ {pap is to prevent grease front the dish water entering tl1e septic
mill tank and disposal lines. An excessive 2lll10l1lll of grease tends
lll ` to decrease the cllicictlcy of the lZllll{ by retarding bacterial
“""` Z action illltl may clog thc disposal llllt'S. The use of grease traps
ll"'   is advised altho septic tanks haxe been operated successfully
l“"’ j without theni. They add little to tl1e cost of illl installation.
"l'“" Plans for inaking a (‘(lllL‘l'(‘l\’ grease trap are NllU\\'ll in iigure 2.
vent i
E an I Dimensions for Single—Chambcr Septic Tank
2 lllSl(l(3 Dimensions in feet
E Depth below water
j Number of persons Length \\`idth line
2»- 6 5 Blk 3%
7-lo 6 3 4
p  V 1l—14 S 3 4
ip Sis: of Tan/1·. 'l`l1e ta11k shown i11 Fig. Sl is tl1e size required
 1 for a family ol` two to six persons. l)llllt’llSl(lllS for tanks with
° a greater capacity are given i11 tl1e il<'t'Ulll]*illl}`lllQ table. A septic
lEllll{ gives the best results if the capacity below tl1e overtlow
' pipe is sutlicient to hold a 2-days` tlow ot` sewage. allowing 23
‘ gallons ot` water per person per day. No tank Sll(>llltl be con-
  structed snialler than that for ti persons. \\'hen a septic tank
l  V is to be built for tl1e use of a school. hotel. or similar institution,
I special plans should he obtained from a sanitary engineer.
l s ]Z‘.I`('lIl'(l{l.Ull. 'l`l1e earth may he used as the outside form for
= ` llll* tank. The walls of tl1e excavation should he smooth and
I  _ plnnih so as to give a uniforin thickness to the walls. The width W
{ E and lt‘llKlll of lll(‘ excavation should he tl1e SZUIIC as tl1e cor-
'__] T l`t‘S[l(l1llllllQ_’ outside (lllllt‘llSl(lllS of the tank. The depth should
1 he 6 inches greater lllilll tl1e total overall deptl1 of the tank to .
AN 1 Derinit a till of ti inches ot` earth over the top of the lillll{. The
hm sink '  th ot tl1e excavation may be influenced by the depth of the
ll" wml ll‘lll*t‘ sewer outside of the l1onse foundation. the £llll0lllll ot fall
._ i11 the ground between the l1onse a11d the septic tank Hlltl the
1st out- Q 1nini111n111 llllltllllll of tall required in tl1e sewer from the house
itlrltlsc ` to the tank as l'(‘('(}llllllt‘l\(ll‘(l (lll page S under the lwiltllllg
enip 105 V
s

 l  
10 Kcrzlnclry Extension ('i1·cuInr No. 131  
"Sewer Line". It is always advisable to take level readings for
the purpose of securing the necessary information exactly before —
the depth of the excavation is permanently lixed. l
Inside Form. The inside form for the septic tank should
be made so that it may be removed easily after the concrete has .
set. Plans for its construction are shown in Fig. ll. The form  .
should be assembled above ground and lowered into place in 4
the excavation where it is held by cross-pieces resting on the
top of the ground. The bottom of the form should bc t$" above
the bottom of the excavation. 'l`he inlet and outlet 'i"s aaai I
their connecting pipes should be set in place before the concrct-·
is poured into the forms. In order that the inside form inay  i
be removed easily the top tive boards at each end should not e
be nailed in place, otherwise the ends will be hard to reniove  
because of the inlet and outlet T`s. The cross braces at the top. '
center and bottom of the tank should be carefully placed so as
to avoid spreading of the form which would cause a thicker V
wall than necessary. Before the form is lowered into place I
the outside surfaces should be well oiled. This will make the
` removal of the form less difficult; and prevent the concrete from
adhering to the wood. The inside form may be used for sev- »
eral tanks if the work of assembling and taking apart is d··i;·· V
properly.  .
Top Slabs. The slabs for the concrete top should be ca~t ·
in special forms and moved to the top of the septic tank alter
the tank form has been removed. Three 1/t" steel reint`orcin; .
rods are required in each 2-l-inch slab, to prevent cracking. -
These rods arc embedded in the concrete, 1 inch above the bot- i
tom of the slab, as shown in the section view of a septic tank. T
Fig. 3.
Mixing and Placing Concrete. If the sides of the excavation
are to be used as an outside form, care must be taken to prevent V
dirt from falling into the concrete as it is being placed. A frame
of 1—inch boards around the top of the excavation, as illustratetl A
in the isometric drawing, Fig. 3, will keep dirt out. These boards
may be placed before the work of excavation is begun.

  ¤ Septic Tun/rs for Sewage Disposal 11
E5 {UF The walls of thc septic tank must be water-tight; therefore
iofwrc ‘ considerable carc should bc talccn to make a water-tight con-
i crctc. Both iinc and coarse aggregate should be free from
`hould sediment. The tinc aggregate or sand may contain particles
tc has p as large as {Q" in their grcatcst dimensions and the coarse
{Om  Y aggregate or rock should not contain pieces larger than 1 inch.
me in ’ The concrctc should be mixed until all particles are covered
m mi with a ccntcnt-sand paste,
HUM The following instructions for making water-tight concrete
lc hm _· for a septic tank were prepared by the Portland Cement Asso-
’m_m__ ciation. They apply to mixing concrete for the top slabs as
H mm  ` well as for the walls and bottom.
ld mg; - "ln order to produce water-tight concrete it is necessarjv
..&,mU._-L, T to regulate thc amount of water that is 11sed with each sack of
he Mp ‘ cement. as it has been proved that not only the strength but also
It SO as the watertightness oli concrete is controlled by the proportion of
www , water and cement in thc mixture.
) place I "l·`or a water-tight mixture it is recommended that not
lk.- th.; more than ti gallons of water be used with each one-sack batch.
_c from This water includes the moisture which is carried in the sand,
by sev- » as this moisture is free to react with the ce111ent. ljsually sand
is l]..;;»· V is damp o1· wet and contains approximately {Q; gallon of water
 . in each cubic foot. The correct amount of water to add in a
lm UN V onc—sack batch, using wet sand, is 5 gallons, This allows for
lk MM one gallon of water in the sand that would be used in the 1111X.
\i.m_(_m; A lhns gallon, plus the 5 gallons added to the mix. makes a
mckimp _ b—:allon paste which is recommended for water-tight L‘O1lCl`€l€‘. .
thc bm . "lti the sand used is absolutely dry the full 6 gallons of
ic muh T water are added, since there is no moisture in the sand. \\`hen
the sand is slightly moist but not wet enough to form into a ~
_ hall when compressed in the hand, 5% gallons of water are
mmlloll . added for each one-sack batch, Usually, however. sand is wet,
P1'°"°“l in which case the proper amount of water to add is 5 gall011S
A {mw for each sack hatch. In ease half-sack batches are used only
uslmlml ·   gallons ol` water are added.
C bomidl "As a trial mix with ordinary wet Stllltl use one sack of
portland cement, 21/, cubic feet of sand, 3 cubic feet of pebbles,
~ .

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Fig· 3· ]`liLllS fur (1 5\]1gl•;-4·]1;111111cl` 1.111W 0

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~ gz FORM BOARDS D0 NOT COME QUITE TO COQNEQS
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Z was   itk
' NOTE METHOD OE BEACE NOT NAILED
NAILING COQNER5 TO YOQM; HELD IN
T; xg .- 4]::  TO MAKE YOQM5 PLACE DY YEES-  :4]
M ` { H g  ASILY IZEMOVABLY. 5URE OY CON   Zi E
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PLAN OF INSIDE FORMS
I I  
Aszwnw /0 '   • ._
DUTLET       K ’ J   I
I \· { A   K *
TOP FIVE END BOAQD5 O II  7 gi?
‘ LOOSE EOQ INLET AND   " _ ~ ll \,\5`h .  
Y OUTLET FITTINGS `\   ¤f»»Q ‘
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_ // METQIC QAWING
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4
IL  DIMENSIONS AND MATERIALS
¤· SINGLE CHAMBER SEPTIC TANK
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1-L 1fcau‘uel.·y Extension Circular No. 131  
and 5 gallons of water. These are mixed together thoroughly  
at least two minutes in a drumtype mixer. lf the resulting  
mixture is quite wet add slightly more sand and pebbles, say  nv
lg cubic foot of each, and re—111ix and again examine the mixture  Y
to see if it has the right degree of plasticity to work well when  
placed in the forms. lt may be that the first trial batch is too  
stiff to handle readily, then slightly less quantities of sand and  
pebbles should be used in the next batch. ln this way, the  
correct proportions of sand and pebbles for the job are deter-  j
mined.  ·
"In a good, workable mix there is sufficient cement and  
mortar to fill all spaces between the pebbles or crushed stone.  3
Such a 1lllXllll'Q holds together and there is little tendency for  
the fine and coarse material to separate. A good, workable mix  
will place in the forms readily with light tamping and will  
produce smooth surfaces when forms are removed. A good »_ 
method of testing the 1nix to see if it contains sufficient mortar  
is to draw a shovel or trowel across it. If the spaces between  E
the pebbles are filled with mortar the mix is satisfactory. lf  
- the spaces are not all filled, there is not sufficient mortar and the  _
concrete will be hard to work, will be of rough appearance, and  
will not be water-tight."  
A The bottom of the tank should be placed first and the walls  
last so that no joints are left between floor and walls. The con-  
crete should be placed and thoroly spadcd as soon as it is mixed.  
The purpose of spading the concrete is to work the larger  
’ particles into the concrete mass and away from the forms sc  
the surface of the walls will be smooth. Overspading raises if 
coarse particles to the surface and produces an uneven concrete. f 
In warm weather the inside form may be removed after 24  
hours. lf the form is left in place too long the boards may  i
swell and be hard to remove.  €
THE DISPOSAL SYSTEM  
The disposal system is a line of agricultural drain title `_ 
into which the overflow from the septic tank is conducted, , 

 l
  Septic Tait/rs for Sewage 1)[spo.sul 15
  nsnully thrn u line of sewer pipe. Sewuge enters the soil thru
  theopenjointst1l':tg‘t‘i\ill`}' lll ]1l't1l¤‘¤‘l il N‘*lll'|'Q' Ull \\`Illt‘l' lll|‘ >t‘\\`<‘1' lllltf lllily
  lie einittetl uml the tlispnsul line eonneetetl tlireetly to the tuuli.
ir  The sewer line lemling from the septie tunl; usnully is composed
_  of l" pipe with eulketl uml eeinentetl 'l<)ll1lS. As this line eurries
 A no snlill niutter the grmle neetl not exeeetl U" to u l1u11drcd feet.
  ])i`sp»s·i/ Lim, The tlispnsul line nr ultsnrptioit system
  slintiltl he lneutetl on well tlruine·l soil ut leust 150 feet from any
Q  well, spring or eistern, The luml nn wlneh the disposal bed is
  lneutetl sl1¤·l1l -
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_ Fig. 5. A strip of tarrod vapor, 6"xl2", should ho uspd lo ··o\·.»i· .·;m_
joiiit in the disposal line so as to pr¤~\‘cnt {ho lin~· from \u···oming (ill.-d wml,  ·
SOI .  ~
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Fig. G. Method of laying tile in a tight soil, I
If the soil in which tho disposal lim- is laid is not opou and  p
porous, the rate of absorption by the soil may bo iiu·rvas¤—d lll
laying the tilc on a bod of gi-ax cl, crnshr-d rock or (‘l\\(i(‘l`S 21-  _
Sl1OWI1 in figure 6. To [)I`(¥V(‘llt the drain tilo from golfing: Olll  _
‘ A

   Septic Tanks for Sewage 1)isp0sal 17
HS   of line because of uneven settling the bed of porous material
  should he well taniped before the tile is placed on it. The bot-
  tom of the trench should he graded and the cinders placed to
  an even depth thrnont the length of the trench.
.7,   (fare of a, Ntptie Tun/r. After the form has been removed,
i  in the tank should he lillcd with water. lt is then ready for use.
`{QT`,}  . An erroneous idea exists that a "startcr" in the form of horse
 }_ nianure should he put into the septic tank. This is not neces-
 ‘ sary, tfheiuicals of all kinds shouhl be kept out of the tank.
   i The ordinary amounts of cleaning and washing compounds used
_.     aliout the house do no harm. Nothing more substantial than
Y it  lj toilet paper should he permitted to enter the tank as resistant
if     materials may pass thru the tank Hlltl cause the sewer or dis-
’ l  j; posal line to hecome clogged.
  l   A septic tank may need cleaning after six or seven years’
    operation or when the sludge has attained a depth of iS inches. {
Jl .  The senin. water and sludge may lie removed hy a diaphragm
`Ql-`fti§   pump. and linried or plowed under in a field or pasture hut,
  never emptied into 2111 open stream or deposited i11 a garden.
   » THE SEPTIC PRIVY
.i`:‘   ln l·`ig. T plans are shown for a septie privy which Serves
   _' as an outside toilet where inside toilet fixtures are not used hut
    \vlie1‘e a kitchen sink and pump are in use. The waste from the
M   kitclien sink after passing thru a grease trap. as shown in Fig.
3  . 2. is drained into the vault of the septic privy. This disposes
.4,, _Q  (tf \\'t1SIt‘ Water and provides water to promote the liqtlef21t‘ti0l1
    of solids in the vault,.
h•';'€  if Wliere the house over the privy vault is kept clean Zllltl
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