HOUSE DRAINAGE.
=The Removal of Impurities.=—In order that health may be maintained in
any inhabited house, it is essential that the impurities produced by
animal life should be removed. These impurities may be divided into two
classes—the first including the gaseous and volatile products evolved
from the lungs and skin; and the second, the liquid excretion from the
kidneys, and the solid from the bowels. The former are got rid of by
efficient ventilation and by cleanliness; the latter, ought to be as
quickly removed, but require more elaborate arrangements to ensure this.
The =average daily amount= of solid excreta is about 4 ounces, and of
fluid excreta about 50 ounces for each adult male. Taking all ages
and both sexes into consideration, the amount per head is about 2-3∕4
ounces of fæces and 32 ounces of urine. When dried, the daily fæces
amount to 1·04 oz., the daily urine to 1·74 oz., so that the manurial
value as well as the possible polluting power of urine is much greater
than that of the fæces.
After a variable interval urine and fæces begin to decompose, ammonia
and fœtid gases being disengaged in large quantities. Urea the chief
constituent of urine is decomposed into carbonic acid and carbonate of
ammonia. Thus
CH₄N₂O + 2H₂O = (NH₄)₂CO₃
In addition to the excreta, house-slops have to be got rid of, and
“dust.” =House-slops= vary greatly in quantity, but probably amount to
as much as sixteen gallons per head daily. They consist chiefly of the
water used in cooking and washing and for baths. It would be a mistake
to suppose that only urine and fæces need careful disposal. There
are masses of decaying epithelium from lavatories and baths, organic
matters from soiled apparel, and various organic matters from culinary
operations, all of which may cause serious nuisance unless promptly
disposed of.
The =Dust= consists chiefly of the ashes from fires; but the dust-bin
also forms a favourite refuge for kitchen refuse, composed of various
animal and vegetable matters, as well as for broken pots and tins. It
is dealt with apart from the house-slops and excreta, except in certain
dry methods of disposal of sewage.
Two chief plans of getting rid of the sewage have been proposed, though
there are many varieties of these. They are—
1. The Water Method, and
2. The Dry Methods.
For towns the water carriage of sewage is indispensable, and in this
chapter we shall confine ourselves to the part of this system which
relates to the =Drainage of the House=.
The chief sanitary appliances of a house, which empty their contents
into the drain and thence into the street sewer, are—(1) Rain-water
Pipes; (2) Bath-room and Sink-pipes; (3) Water-closets; (4) Soil-pipes;
and (5) The House Drain. We will consider these in detail.
=Rain-water Pipes= collect the water from the roof by means of gutters,
and carry it down to the house drain, except in the few cases in which
the rain-water is collected for use. The rain-water or stack pipe was
formerly joined directly at its base with the underground drain. This
was evidently bad, because the upper end of the pipe was frequently
near windows, and foul gases from the drain might be conducted by it
into the house. It is equally objectionable to connect the rain-water
pipe with the soil pipe and for the same reasons as above.
_The general rule with regard to all pipes carrying away water from the
house, with the sole exception of the soil-pipe, is that they must be
disconnected from the underground drain and discharge into the open air
over a gulley-trap._ This rule applies to
rain-water pipes, and to
waste pipes from baths,
lavatories,
sinks.
It does not apply to the soil-pipes leading from
water-closets and
slop-sinks,
which must discharge directly into the drain.
Overflow or waste-pipes from cisterns for drinking water or from
cisterns for flushing w.c.’s or to safe trays under the seat of
water-closets should all be made to discharge into the open air, where
the leakage can at once be discovered.
The form of gully-trap to be used at the junction with the drain is
described on page 167.
=Other Waste-pipes= as from bath, lavatories, and sinks, must be
similarly disconnected from the drain, and made to discharge over
gully-traps. When the pipe leading from the bath, lavatory basin, or
sink, is long, it is apt to become foul from the accumulation on its
inner surface of slimy matter, consisting of soap, dirt, and other
offensive matter. For this reason it is wise to have a syphon bend in
the waste-pipe near its junction with the sink or basin. Such a trap is
shown in Fig. 19.
The syphon bend alone in the waste-pipe without disconnection from the
drain at its lower end would not suffice to ensure complete absence
of nuisance, especially for sinks and lavatories which may be disused
for a considerable period. Under these circumstances the water in
the syphon trap may become evaporated, and then foul drain gases be
wafted into the house. Furthermore, even if the water in the syphon
trap remained, foul gases may be absorbed from the drain and given out
at the end nearest the house (_a_, Fig 19). Hence it is always best
to disconnect all waste-pipes from the drain, except the soil-pipe
which cannot be treated in this way. The waste-pipe from the upstairs
lavatory or bath may be made to discharge over a hopper-head and thence
into the rain-water pipe, which is disconnected below from the drain.
This plan should only be adopted when the hopper-head is not close to a
bedroom window.
[Illustration: FIG. 19.
SYPHON TRAP UNDER SINK, WITH SCREW-OPENING FOR CLEANSING.]
Under the bath is usually placed a leaden tray, called a _safe_, to
catch any accidental spillings of water. The overflow pipe from this
safe should discharge direct into the open air. Formerly much evil was
caused by allowing waste-pipes from baths, sinks, and lavatory-pipes,
or overflow pipes from drinking-water cisterns or from the bath-safe,
to be connected directly either with the trap of the w.c., or with the
soil-pipe beyond it.
[Illustration: FIG. 20.
A. STONEWARE GULLY-TRAP.
B. SECTION OF THE SAME, SHOWING A WATER-SEAL 3 INCHES IN DEPTH.]
=Sinks= are not uncommonly the source of offensive smells, when made
of wood or stone. A hard glazed sink should be provided; as this is
non-porous and can be kept clean. The sink should be placed against an
external wall, so that the waste pipe can be carried through the wall
to a gully-trap outside the house. Formerly the sink-pipe was joined
below directly into the drain, the only obstacle to the entry of sewer
or drain gases into the kitchen being a bell-trap at the sink. This is
quite insufficient for the purpose. The waste-pipe from the sink should
have a syphon trap under it, with an inspection opening at its lowest
point (Fig. 19), and should discharge in the open air over a gully-trap
(Fig. 20), as in the case of rain-water and bath-waste pipes. It is
usually stated that the waste-pipes from sinks, etc., should discharge
at least 18 inches distant from the grating of the gully. This is
too far, because some of the foul water may become dried up in the
channel, and its solid particles be blown about. They may be allowed to
discharge directly over the grating of the gully (Fig. 20) or even into
the side of the gully below the grating, but above and on the house
side of the water-seal shown at B. Fig. 20.
The gully-trap is connected with the socket of the first drain-pipe,
and the junction is made water-tight by means of a cement joint.
On this account, and because it gives a better water-seal than the
bell-trap or D trap, the gully-trap should be always used. The best
form of gully-trap, the P trap, is shown in Fig. 20 B. This is better
than the S trap (Fig 19), which involves a bend in the drain at its
junction with the trap.
=Water-closets= require to be skilfully constructed and well-situated,
if they are not to become a serious nuisance. In building a house, the
_position_ of the closet should be carefully considered. In all cases
it should be in an out-standing part of the house, against an external
wall, and separated from other parts of the house by a passage,
preferably a passage which is cross-ventilated. Instead of this, one
commonly finds it in any convenient recess, abutting on a bedroom, or
where it cannot be properly ventilated. Usually the closet is placed
at the back of the house; and as the main-sewer is generally situated
in the front street, it follows that the drain must in terrace houses
pass under the house. Hence the importance of having it completely
water-tight. Water-closets in bathrooms are very inadvisable.
The _ventilation_ of the closet should be good—if possible, by two
opposite windows; and where practicable a cross-ventilated lobby should
intervene between the closet and the rest of the house. This is now
always provided in hospitals.
The _water-supply_ to the closet should be abundant. Every flush of
water should be sufficient to carry the contents of the basin through
the soil-pipe and the drain into the sewer. The quantity allowed by the
Water Companies in London is two gallons, which is barely sufficient
for this purpose, unless the form of closet pan is good, and the
down-pipe to it of sufficient diameter. Each closet should have a
separate cistern, the best being the so-called “water-waste preventer,”
by means of which a certain quantity of water, and no more, can be
discharged each time the handle is pulled. One of the best of these is
shown in Fig 21. When the handle of this is pulled, the whole of the
water in the cistern is syphoned out by the syphon and carried down to
the water-closet, whether the handle be held down or not.
The amount of fall from the cistern to the closet should not be less
than four feet, and the pipe should be free from bends in order
to ensure a thorough scouring of the trap and soil-pipe; and the
flushing-pipe should have an internal diameter of not less than 1½
inches. It is commonly supposed that a small flow of water, trickling
continuously down a closet, tends to keep it clean, and prevent
smells; but the water thus used is simply wasted. Others fasten up the
handle of valve-closets so as to allow a large flow of water. This does
not answer the desired end, and renders the offending person liable to
a penalty for wasting water.
Many different forms of water-closet are in use. In all of them the
main requisites are that there should be (1) a good flush of water, (2)
a rapid removal of the excreta, and (3) no possibility of reflux of
gases. The chief varieties of closets are the pan, valve, wash-out, and
wash-down closets.
[Illustration: FIG. 21.
SYPHON FLUSHING CISTERN.]
In Fig. 21 a portion of the bell of the syphon is shown cut out,
so as to display the movable plug at the bottom of the cistern. An
objectionable feature in most cisterns is their noisiness in use. In
the above cistern, the pipe admitting water is carried down to within
an inch of the bottom of the cistern, thus ensuring noiseless entry of
water.
=Pan-closets= (sometimes called _double-pan closets_) are essentially
bad, though largely employed in the past. The construction is shown in
Fig 22. Below the conical basin there is a metal pan capable of holding
a certain amount of water, the lower end of the basin dipping into
this water. By means of a pull-up apparatus the contents of the pan
can be tilted into a second larger pan or _container_, and the bottom
of the container is connected by means of a short pipe with a leaden
[bowl-shaped symbol] shaped trap, from the side of which the soil-pipe
passes out to be carried down to the drain. The arrangement insures the
production of nuisance. The container and [bowl-shaped symbol] trap
always arrest a certain amount of foul matter; and each time the handle
of the closet is pulled up a puff of foul air comes into the operator’s
face. Occasionally the [bowl-shaped symbol trap becomes corroded by the
filth it contains, and foul gases from the drain escape into the house.
[Illustration: FIG. 22. INSANITARY PAN CLOSET, SHOWING D TRAP BELOW.]
=Valve Closets= differ from the last in having no container, but only
a small box containing a movable water-tight valve, exactly fitting
the lower edge of the basin (Fig. 23). They are much superior to the
pan-closet, but require an overflow pipe in order to avoid accidental
flooding of the closet. The overflow pipe should be made with a syphon
bend in it, and the flushing of the closet should be so arranged that
each time it is performed water enters the overflow pipe. (See Fig.
23.) The trap below the valve should be in the form of a syphon (see
under traps, page 179), as this is not easily fouled. It is preferably
made of lead, securely jointed to the soil-pipe and to the valve box
of the closet. A lead tray or “safe” is required on the floor beneath
a valve closet, in view of accidental spillings or overflow; and this
should be provided with an overflow pipe discharging into the open air.
[Illustration: FIG. 23.
VALVE CLOSET.
=A—Pan=. =B=—Overflow pipe with syphon trap. =C=—Valve shut.
=C₁=—Valve open. =D=—Valve box. =E=—Floorline. =F=—Water-seal of trap.]
=Valveless or Hopper Closets=, of which the =Wash-out, Wash-down and
Syphonic Closets=, are the chief forms, present certain advantages over
the valve closet. There is less apparatus to get out of order and no
metal to become foul. They do not require an overflow pipe, as water
can escape freely through the trap of the closet. Valveless closets
need not be encased by wood-work, thus ensuring freedom from spillings
of foul water, and they are more easily used than valve closets for the
discharge of bedroom slops, thus obviating the necessity for a special
housemaid’s sink. Valveless or hopper closets are cheaper and simpler
in use than valve closets, and when in use are equally sanitary. If a
house is left empty for a considerable time, the water in the trap may,
however, become evaporated, an event much less likely to occur with a
valve-closet. The latter are furthermore less noisy when flushed. With
a valve to hold up the water in the pan, as in the valve-closet, a much
larger quantity of water can be retained than with a hopper closet.
Hence the importance of the latter having such a shape as shall prevent
fouling of the basin by fæces.
One of the older hopper closets was the =long hopper= shewn in Fig.
25. In this form the pan is conical in shape, its sides necessarily
becoming fouled by its use, and the spiral flush, the point of entry of
which is shewn in the figure is quite insufficient for cleansing the
pan.
Of =Short hoppers= the best has a nearly vertical back as shewn in Fig.
24, a rim-flush, by means of which at least two gallons of water are
discharged with the fæces, and the pan is thoroughly cleansed.
[Illustration: FIG. 24.
RIM FLUSHING WASH-DOWN BASIN.]
The =wash-out closet= is shewn in Fig. 26. In it a certain amount of
water is kept in the upper part of the pan by a ridge over which the
fæces have to be driven before entering the trap. The force of the
flush is thus broken. In this closet a large area is liable to be
fouled, and it is now almost entirely disused.
[Illustration: FIG. 25.
SHORT HOPPER CLOSET. LONG HOPPER CLOSET WITH SPIRAL FLUSH.]
=Syphonic water-closets= are wash-down closets, in which the flushing
out is aided by syphonic action. They need to be fitted with a flushing
cistern, giving an after-flush as well as a flush; otherwise the basin
is left untrapped. One of the most elaborate closets of this type
is Jennings’ Closet of the Century. Fig. 27 shows that the flushing
cistern has two connections with the closet, one in the usual manner
with the flushing rim of the pan, the other connected to the long arm
of the syphon (A Fig. 27). B is a puff pipe allowing the escape of air
from this syphon when started. Thus while one part of the flush scours
the basin, the other expels the air from A through the puff-pipe B,
fills both arms of the syphon with water, and thus starts the syphonic
action by which all the contents of the basin are sucked out of it.
In this form of w.c., syphonage is intended to be produced, and the
after-flush prevents the w.c. from being left untrapped.
[Illustration: FIG. 26.
WASH-OUT CLOSET.]
[Illustration: FIG. 27.
SYPHONIC CLOSET.]
Syphonic water-closets appear to me to be unnecessarily elaborate and
complicated, and the only advantage over the wash-down closet is the
deeper layer of water in the basin. With a well-shaped wash-down closet
this is of little importance.
In other forms of wash-down w.c., =unsyphoning= may also occur, for
instance, by pouring the contents of a slop-pail into the pan. This
is particularly apt to occur, when two or three water-closets are
on different floors of a house, one over another. This unsyphoning is
prevented in the case of the highest w.c. by the soil-pipe ventilator,
but not always for the lower w.c.’s. For these it may be necessary to
carry a pipe from the highest point of the trap of the closet, where
it joins the soil-pipe, through the wall into the external air. Such
a pipe is called an _anti-syphonage pipe_ (Fig. 28). It effectually
prevents the water being sucked out of the trap of a lower w.c. when
the w.c. on a higher floor is being flushed.
[Illustration: FIG. 28.
A—Elevation. B—Section through wall of house, showing connection
of w.c.’s on three floors, with soil-pipe and anti-syphonage pipe.
_b_—Junction of closet trap with soil-pipe, _a_ being a P and
_b_ an S trap. _c_—Junction of soil-pipe with earthenware drain.
_d_—Anti-syphonage pipe, seen best in elevation A. _e_—Soil-pipe.
_f_—Anti-syphonage pipe. _g_—Underground drain. _h_—Soil-pipe
ventilator. _i_—Cage-work protecting top of _h_. _j_—Point at which
anti-syphonage pipe is connected with soil-pipe ventilator, above the
highest w.c.]
In the forms of w.c. already described, clean water is used for
flushing, and we have seen that two gallons, the quantity usually
allowed, does not suffice for this purpose, unless the closet pan is
of the best possible shape, and the service pipe sufficiently wide to
project the water by means of a rim-flush forcibly over the pan and
into and beyond its trap. Other forms of w.c. have been employed of
which the most important are slop-water closets, and trough-closets.
In =Slop-Water Closets= the waste water from sinks and baths is
utilised for flushing, and thus a saving of water is effected. This
form of closet is used considerably in manufacturing districts, and is
less liable to freeze than an ordinary w.c. The sink discharges on to
a gully in the usual manner, but the outlet of this gully is connected
with a tilting vessel or tipper, holding 3½ gallons in Duckett’s
closet, which is the best known of this type. The tipper is balanced
on brass bearings, and tips over when full, discharging its contents
into the closet trap, which is thus flushed. The slop-closet is a great
improvement on the privy-middens or pail-closets, which in some towns
it has superseded, but is not so cleanly as an ordinary w.c.
=Trough Closets= are also known as “latrines.” The best type consists
of a glazed earthenware trough under a series of w.c. seats. The trough
is slightly inclined towards the outlet, at which is a weir, beyond
which is a trap. An automatic flushing tank connected with the upper
end of the trough and five to six feet above it, discharges water at
intervals and drives the fæcal matter over the weir and through the
trap. This form of closet is only suitable for factories. It is to
be deprecated for schools, and even for factories, unless there are
exceptional reasons for its continuance, as fæcal matter possibly of an
infectious character may be retained a considerable time in the trough.
The domestic =Slop Closet= or “housemaid’s sink” must not be confused
with slop-water closets mentioned above. The slop-closet or sink
is used for emptying the contents of bedroom pails. These being
necessarily foul and liable to early putrefaction must be treated
exactly like other sewage matters. An ordinary pedestal w.c. with
a lift-up seat answers excellently as a slop-closet; but in large
houses and public establishments a separate slop-sink is desirable
with a larger surface than most water-closets. The slop-closet must be
connected with the soil-pipe, just in the same way as a w.c.
[Illustration: FIG. 29—SECTION THROUGH A HOUSE FROM FRONT TO BACK
SHEWING DRAINAGE ARRANGEMENTS.
_A._—Sewer; _B._—Intercepting trap; _C._—Cleaning eye for pipes
between chamber and sewer; _D._—Inspection chamber; _E._—Inlet
ventilator; _F._—Gully-trap for forecourt; _G._—Air-bricks
for ventilation under floors; _H._—Damp-proof course[8];
_I._—Concrete 6” thick over site of house; _J._—Drain, fall 1 in
24, imbedded in concrete; _K._—Soil-pipe carried up full size
above eaves; _L._—Upstairs w.c.; _M._—Gully-trap receiving water
from _N_ scullery-sink, _O_ bath and _P_ rain-water stack-pipe;
_S._—Ventilating pipe at upper end of drain; _T._—Pipes leading to
same.
] =The soil pipe= is the vertical pipe carrying the contents of the
water-closets in the drain. It must be distinguished from the drain,
which is chiefly, if not entirely, underground. The exact position of
the soil-pipe and its relation to the drain can be seen in Fig. 28 and
29, which should be carefully studied. The soil-pipe should be made
of drawn lead without seam, of uniform thickness throughout, and of at
least 7 lbs. or better 8 lbs. weight per superficial foot. Any joints
in the lead pipe should be of the kind known as “wiped,” not a “slip”
joint. The outside of a wiped joint is shewn in Fig. 30B. Iron pipes if
used must be 3∕16 inch thick, and have sockets sufficiently wide and
strong to permit of the joints being caulked with molten _i.e._ “blue”
lead, in the same way as water-mains are laid.
The soil-pipe should be throughout its course under observation. It
should not be built into a wall, where it might be accidentally pierced
by nails, nor within the house, allowing foul gases to escape from weak
points in the joints. It should be carried through the wall of the
house immediately beyond the closet trap.
The soil-pipe should not be more than four inches in diameter. It
should be continued from its highest point at the junction with the
closet-trap above the roof by a pipe of the same diameter, with its
end wide open (Fig. 29 K). This _ventilation of the soil-pipe_ is
essential (_a_) to prevent the entry of foul effluvia into the house,
especially when the water in the closet-trap is dried up; (_b_) to
prevent unsyphoning of the upper by the lower water-closets in a house.
(On this point see p. 172).
[Illustration: FIG. 30.
A.—SECTION SHOWING A GOOD METHOD OF CONNECTING SOIL-PIPE TO DRAIN BY
BRASS THIMBLE.
B.—OUTER VIEW, SHOWING BRASS THIMBLE WIPED ON TO SOIL PIPE.]
The upper end of the ventilating pipe should be made to open remote
from any window. It may have a cowl attached to it, but it is doubtful
if this materially aids the aspiration of foul gases. It is wise to
cap the upper end of the ventilating shaft with a dome of large meshed
wire-netting to prevent birds building their nests in it.
The connection of the soil-pipe with the closet-pan is its weakest
point, and the most liable to leak. The main difficulty consists in
forming =joints between earthenware and metal=. Socketed connections
are not safe. The use of an india-rubber ring inserted between the
lead and earthenware flanges and bolted together by means of a brass
collar and hooked bolts makes a fairly good connection. Various screwed
connections are made. In another form the earthenware collar is covered
outside with lead, so that a soldered joint can be made between the
earthenware trap and the soil-pipe. In the “metallo-keramic joint”
the earthenware joint is painted over with a metallic solution and
fired. To the metal film thus formed, lead or other metal can be firmly
soldered.
The connection of the soil-pipe into the socket of the first pipe of
the earthenware drain requires also to be carefully made. This pipe is
curved, and at its upper end has a socket, into which the soil-pipe
enters. A length of brass or copper tubing known as a “thimble” (about
a foot long) should be soldered to the bottom of the soil-pipe; the
rim of this thimble rests in the socket of the drain-pipe and the
space between the two is filled with Portland cement (Fig. 30A). With
the ordinary connection between lead soil-pipe and drain, the former
is apt to become dented by blows, and the latter is very liable to be
partially blocked by the dropping of cement inside the pipe when making
the joint.
=The House Drain= under ordinary circumstances receives waste water
from sinks and baths, rain-water, and the discharge from the closets.
[Illustration: FIG. 31.
SHOWING DEPTH OF FLUID AND CONSEQUENT FLUSHING FORCE OF THREE DRAINS
CONTAINING AN EQUAL QUANTITY OF SEWAGE.]
We may consider drains under the following heads: material, form,
joints, gradient, ventilation, trapping. The first essential is that
they should be water-tight, so that their contents do not percolate
into the surrounding soil. _Socketed glazed stoneware pipes_ and
_iron pipes_ best fulfil this condition. The best material for making
stoneware pipes is Devon or Dorset, or similar fine clay, which makes
a very strong pipe. Tested pipes free from cracks and flaws must alone
be used. The pipes should be laid in straight lines, each pipe being
arranged with the spigot and not the socket end directed towards the
flow of sewage. The fall should not be less than 1 foot in from 40 to
60. If the fall is less than this amount, artificial flushing from
the upper end of the drain is necessary. Usually branch drains are
made 4 inches in diameter, the main house-drain having a diameter of
6 inches. A larger size than this is seldom necessary. Thus if A, B,
and C be three drains with an equal fall and conveying an equal amount
of sewage, the rate of travel and therefore the flushing force will be
greater, because the depth of the fluid is greater, in A than in B,
and in B than in C. Small drains are more completely self-cleansing
than large drains. The water-tightness depends on the character of the
joints. In this respect _iron drains_ present the great advantage over
earthenware that there are fewer joints and that these can be rendered
permanently water-tight without difficulty by being run with blue lead
and well caulked. To render an earthenware drain water-tight, (_a_) it
must be laid on a solid bed of cement concrete at least 6 inches thick,
so as to prevent sinking, and under the house it should be covered with
an equal thickness of cement concrete (I, Fig. 29). (_b_) The joints
must be made with extreme care, the best Portland cement being used for
the purpose. Clay is inadmissible, as the fibrils of tree-roots easily
find their way through it. The inside of the joint must be raked by the
workmen, before the next pipe is laid, to make sure that no fragments
of hard cement are left projecting in its interior. Such projections
are not uncommon causes of subsequent blockage. Various patent joints
have been used, but they are no better than the above when properly
laid. Just before the drain leaves the curtilage of the house and near
its junction with the sewer, it is trapped, and on the house-side of
the trap (E, Fig. 29) an inlet ventilator is provided. The general
arrangement should be studied in Fig. 29.
=Ventilation of the house drain= from end to end is important, a free
escape of foul gases out-of-doors being induced. The _exit_ is provided
by carrying the soil-pipe up full bore above the eaves, and remote from
windows. One opening alone would not induce a current of air, and the
other end of the drain being trapped from the sewer (B, Fig. 29) it is
necessary to provide an _inlet for fresh air_ at E. This may be placed
a few feet above the ground or at the ground-level. Usually a mica-flap
valve is provided at its upper end, which closes whenever a puff of
foul air attempts to escape from the drain. The necessity for this is
doubtful. Ordinarily air enters at the inlet and circulates through the
drain, escaping at the upper end of the soil-pipe ventilator.
It has been advocated that the soil-pipe ventilator should form a means
of ventilating the sewer as well as the house-drain, the intercepting
trap in the latter (B, Fig. 29) being removed. This is inexpedient, an
element of risk being introduced, in view of the possibility of the
drain or some of the connections of internal sanitary fittings being
defective.
[Illustration: FIG. 32.
WEAVER’S INTERCEPTING TRAP.]
The drain as ordinarily arranged is trapped from the sewer by an
=intercepting trap=. This is not merely a trap, but a trap provided
with ventilation at its end nearest the house. A form commonly employed
is shown in Fig. 32. B is the junction with the house-drain, at D
is the water-seal, while at C fresh air enters the house-drain. E is
a cleaning eye, through which any chokage can be cleared towards A,
leading to the public sewer. It is important that the intercepting
trap should be accessible in the event of accidental stopping. This is
provided by an =inspection chamber= or =man-hole=. This if close to
the house is provided with an air-tight cover, the inlet ventilator
being conveyed above ground to a convenient point. The man-hole itself
is built with brick set in cement and lined with cement. Note that in
the man-hole itself half-channel pipes convey the sewage instead of
complete pipes.
Sometimes more than one drain-pipe converges to the same man-hole,
and then a more elaborate arrangement than that shown in Fig. 29 is
required, the branch-pipes converging into half-channel pipes in the
man-hole.
=Varieties of Traps.=—Traps are placed at various points of the
house-drainage system to prevent the admission of currents of foul
air into the house. They are all constructed so as to intercept a
water-seal between the drain and the house or yard at the upper end
of the trap. Traps are placed in four positions in connection with
the drainage of a house: (1) near the junction of the house-drain
with the sewer; (2) under the pan of each w.c.; (3) in the open air
at the ground level to receive waste water from bath, sink, and
lavatory basin; and (4) in the waste-pipe close under the bath, sink,
or lavatory, when the waste-pipe is long and apt to become foul; (5)
inside sinks at the upper end of their waste-pipes.
_Intercepting traps_ between the drain and sewer have already been
described. They must always be ventilated (C, Fig. 32 and Fig. 29). A
syphon shape with a water-seal of 3 inches is required, and the trap
should be self-cleansing, that is, whenever the w.c. is used, the fæces
ought to be carried beyond the intercepting trap into the sewer. Other
forms of intercepting trap were formerly used, one of the worst of
which is shown in Fig. 33. With such a trap as this, an accumulation of
filth is inevitable.
[Illustration: FIG. 33.
DEEP DIPSTONE TRAP, WITH ACCUMULATION OF FILTH IN IT.
=A=—Drain entering trap. =B=—Drain leaving trap. =C=—Dipstone.]
=Water-Closet and Slop-Closet Traps= are of the syphon or anti-D type.
The water-seal in these must be at least 3 inches deep, and the trap
must be ventilated by an upright extension of the soil-pipe, otherwise
the water in the trap may be syphoned out when the w.c. is used.
Hellyer’s “anti-D” trap is a lead syphon trap, the calibre of which is
diminished at its bent portion, while the portion of the trap nearest
the soil-pipe or drain is square instead of circular. The constriction
increases the force of the flush of water and thus cleanses the whole
trap, while the square shape impedes the free flow of water, and thus
diminishes the risk of syphonage. Various forms of trap are shown in
Fig. 19 to 34. The most objectionable of these is the old-fashioned
D trap (Fig. 22), the corners and angles of which become fouled, and
consequently the lead becomes corroded.
[Illustration: FIG. 34.
BAD FORM OF TRAP: BELL TRAP.
BAD FORM OF TRAP: ANTILL TRAP.]
=Gully-traps= are placed in the yard, for the discharge over them of
waste-pipes (Fig. 20). A complete disconnection from the drains is thus
effected. Formerly _bell-traps_ were used for this purpose. In the
Bell-trap not much water can get through, the space A becomes blocked
with dirt, the cover B is often taken off and lost, and then the drain
is untrapped; and even without this, the water-seal is very slight, and
the water quickly evaporates.
=Traps under sinks, etc.=, have been already described (page 166).
Traps were formerly placed at the upper end of the waste-pipe of the
sinks when this was directly connected with the drain. Of these the
Bell-trap and Antill’s trap were most common. The Bell-trap has been
described above. In the Antill-trap the trap is not removable, and the
water-seal is deeper than with a bell-trap. This trap is sometimes used
instead of a gully-trap, but is not so good.
=Efficiency of Traps.=—Eassie has said “honestly speaking, traps are
dangerous articles to deal with; they should be treated merely as
auxiliaries to a good drainage system.”
(1) The trap may have been imperfectly laid to begin with.
(2) It may be emptied by evaporation.
(3) Unless the precautions already mentioned (pages 172 to 173) are
adopted, the flushing of one trap may empty another.
(4) The water of the trap may become impregnated with foul gases, and
these then escape on the house-side of the trap. When a sewer becomes
suddenly charged with a large amount of water, as during heavy rain,
sewer-gases may force their way through the intercepting trap. With a
ventilated drain and soil-pipe these dangers are so small that they may
be ignored.
=Unsyphoning= of traps has been already mentioned. It occurs
particularly when there are several water-closets one over another,
connected with the same soil-pipe. The method of preventing it is shown
in Fig. 28.
=The Examination of Drains and Sanitary Appliances.=—This examination
will involve the detection of (_a_) any deviations from the details
of construction and ventilation of drain and soil-pipe, form of w.c.,
disconnection of waste-pipes, already insisted on; and (_b_) any defect
or leakage in any part of these.
1. _Testing of Water-closet._—The interior of the basin or pan may be
painted with a mixture of lamp-black, size and water. If the usual
flush applied immediately afterwards clears this off, the form of pan
and the flushing power are satisfactory. By removing the wood-work
around the w.c., leakage or spillings of slop-water around the w.c. can
be detected.
2. _Testing of the soil-pipe_ may be effected by one of the volatile
tests named under the next heading. To give the test a fair trial, the
upper end of the ventilating pipe should be temporarily sealed over.
3. _Testing of the drain_ cannot be efficiently carried out unless
access can be obtained to the drain near the sewer. In a properly
constructed house-drain a man-hole is provided for this purpose. Two
chief methods of testing drains and soil-pipes are in use, by smoke or
volatile agents and by water.
The _smoke-test_ consists in filling the drains with smoke, the
assumption being that this will find its way through any faulty joint
or trap, thus indicating the site of the defect. Various arrangements
are employed for pumping the smoke into the drain from the combustion
chamber of a pumping apparatus; or smoke is produced by means of
specially prepared rockets. All outlets or ventilating pipes must be
carefully stopped during the operation, and the place where the smoke
is smelt will then indicate any leaky point.
[Illustration: FIG. 35.
SHOWING STOPPER FOR WATER-TESTING OF DRAINS.]
Drain grenades are largely employed for the volatile testing of drains,
the essential constituent being phosphide of calcium. The grenade,
which is attached to a piece of string, is passed beyond the trap of
the w.c., and as the string unwinds the grenade opens and discharges
its contents into the soil-pipe. Or a tablespoonful of strong oil
of peppermint, mixed with hot water, is poured down the highest
water-closet in the house. If this is smelt by another person in the
lower closets, it indicates defective traps or soil-pipe.
All volatile and smoke tests have but a limited utility. They are
useful in detecting defective joints in traps and in the soil-pipe.
They may detect defects in an underground drain; but if no smell or
smoke is perceptible when a drain is tested by this means, the drain
may still be seriously defective. The only absolutely trustworthy
test for drains is the =hydraulic or water test=. The lower end of
the drain is stopped up by a suitable water-tight stopper. Then the
drain is filled with water by means of a tap in the yard, the amount
of water used being approximately estimated by the rate of flow from
this tap. The drain is filled up to the level of the gully-traps in
the yard. If it remains at this level for half an hour, the drain is
sound. More often it leaks so rapidly that it will not fill, or the
level of the water falls quickly after filling, and it is necessary to
strip and repair, or more generally to relay the drain so as to make it
water-tight.
Rats are an important indication of defective drains. The presence of
rats in a house should always lead to a thorough investigation of its
drains.