BAD DRAINS;
AND
HOW TO TEST THEM:
WITH
NOTES ON THE VENTILATION OF SEWERS, DRAINS, AND SANITARY FITTINGS, AND
THE ORIGIN AND TRANSMISSION OF ZYMOTIC DISEASE.
BY
R. HARRIS REEVES.
[Illustration]
E. & F. N. SPON, 125, STRAND, LONDON.
NEW YORK: 35, MURRAY STREET.
1885.
INTRODUCTION.
The impetus given to improvements in sanitary matters by the conferences
held during last year at the Health Exhibition, as well as the desire
shown by engineers and others to improve the sanitary condition of
towns, has induced me to publish the following system of detecting
defects in drainage and sanitary fittings.
It must be admitted that grave errors have been committed by engineers,
architects, and builders, both in planning the fittings of houses and in
laying drains to the main sewers, during the last twenty years. These
errors have been found to have produced serious effects on the public
health. They have also been the means of establishing throughout the
country a number of Sanitary Protection Societies.
These institutions have been the means of saving many useful lives, but
I trust that the day is not far distant when these societies will cease
to exist, and such terms as “scientific plumbers” and “sanitary
arrangements carried out on the most scientific principles” will be a
thing of the past.
To my mind it is a national disgrace to know that in this nineteenth
century architects and builders fixed fittings to houses, and laid
drains from houses to sewers, which affected the health of the occupants
to such an extent that it was necessary to establish insurance offices
to protect persons from being killed by workmen or their employers. What
a page for future historians!
The work or purpose of drains and sanitary fittings is to carry off by
water the soil and dirt from our houses, and it is lamentable to think
that this cannot be done without injury to life.
What should we say if the same precautions were necessary to test or
examine the work of other professions or trades?
To many the system described in these pages may appear new, but it is by
no means so, as it was discovered and used by me in 1880, and was then
the means of finding out serious defects in a supposed perfect drainage
system.
From that time up to the present it has proved of considerable value in
determining any defect in the construction of drains and fittings. With
the detector and anemometer I have been enabled to discover the cause of
so many failures in sewer ventilation, and to trace the origin and
transmission of many cases of zymotic disease.
The object of this work is to place the same knowledge in the hands of
every person connected with sanitary work.
_May, 1885._
CONTENTS.
PAGE
BAD DRAINS, AND HOW TO TEST THEM 1
SEWER VENTILATION 32
THE ORIGIN AND TRANSMISSION OF ZYMOTIC DISEASE 56
BAD DRAINS;
AND
HOW TO TEST THEM.
“Bad Drains.” How often has this term been used during the last few
years? By the medical profession alone, thousands of cases have been
attributed to this cause. To the honour and credit of that profession
its members have thought out and worked out the cause of innumerable
cases of disease under their charge, and rightly fixed their origin to
be due to “bad drains.”
In many cases it has been but a fashionable term to describe cases which
had the appearance of gas poisoning, but did not owe their origin to
drains; but rather to the heated and impure atmosphere of rooms, late
hours, and the sudden change from heat to cold. If there have been a few
hundred cases where “bad drains” were supposed to have caused the
illness and such was not the case, there have been thousands of others
where the disease originated from them, but was taken as a matter of
course, or as one of the frailties of the human frame, when undoubtedly
the cause was “bad drains.”
It is a most remarkable thing, that whilst on the one hand we have the
medical profession energetically working to find out defects in the
planning of drains and sanitary fittings, and writing articles on them,
we have on the other hand surveyors and others who have treated the
matter as a doctor’s fad.
During the last five years scarcely a medical conference has been held
without the question of “bad drains” forming one of the principal
subjects discussed. Medical officers of health have made stirring
speeches and reports to Local Boards; but where is the surveyor who has
had the energy to do the same unless it has been actually forced upon
him? It is a curious but noteworthy fact, that nearly the whole of the
evils of badly constructed drains, and the principal improvements in
them, have been forced on surveyors, builders, and plumbers by the
medical profession and the public.
The reticence shown by surveyors in dealing with “bad drains” may be
attributed to their unwillingness to acknowledge the errors and defects
in works already executed. These works were, at the time, executed
according to the theories adopted by the most eminent engineers in the
profession, and it would be considered unprofessional to admit errors.
There is scarcely a district (excepting where drains have been laid
within the last three years) where the branch drains are trapped into
the main sewers with an efficient water-seal. Surveyors feel that to
acknowledge this would be tantamount to acknowledging a want of
professional knowledge or neglect of duty on their part.
Now, strictly speaking, this could not be the case, and a surveyor
(placed in such a position where he knows that there are defects in his
drainage system, and probably these errors were made by himself,) could
say that these now known defects were not previously known by the most
eminent engineers, and especially with regard to sewer-gas, its
treatment, and action on the public health. Boldly facing the matter and
advocating that the drainage under his charge should be so perfected
that no medical man could point to it as being detrimental to health, if
it entailed an unusual expenditure, coming from the surveyor he would
carry the Board with him, and in doing so would make his position at the
Board doubly secure.
To prove this we have only to refer to reports made by engineers during
the last fifteen years on drainage schemes, compare the results of the
theories laid down, and note the instances in which they have failed,
especially those in connection with sewage farms and the ventilation of
sewers.
I will quote a few extracts from these reports:—
“No injury to health can possibly take place from gas issuing from
properly constructed gratings fixed in the middle of the road, and if
one is a nuisance, dig down and put in others until the nuisance is
removed.”
This has certainly not been the case. You may dig as many holes as you
like, and put in as many gratings, yet some will be injurious to health.
In describing sewage farms, they were described as being (if adopted)
the means of securing a large revenue to the Local Board by the
excellent crops grown, one engineer stating that persons could walk
through them with as much pleasure as through a flower or kitchen
garden; but practical experience has proved this to be incorrect: and
although these statements were made in good faith, they have not been
realised.
You may regulate the irrigation of a sewage farm to such a nicety that
no odour from the sewage is perceptible in the district; yet the
atmosphere will contain poisons which will have a very detrimental
effect on the health of those living there.
For a few years after sewage farms have been laid out, they pay, and you
get good crops from them, but after that the ground becomes so soured
that the farm is almost useless.
In face of these facts no surveyor should hesitate to bring forward
known improvements to his Board.
Many owners of property have recognised the importance of adopting the
best sanitary measures for their houses, although in some cases it is
only a plea to let or sell their property. As an instance of this, some
time ago I was in search of a house in the suburbs, and met with one
described as standing on good gravelly soil, with good drainage and
perfect sanitary arrangements. The builder and owner took me over the
house, and on reaching the kitchen pointed out with some degree of pride
that the sink was cut off from the drains, and stated that the drains
were constructed on the most “scientific principles.”
Now although scientific plumbers have done good work in making our
dwellings more healthy, they have in many cases overdone the matter. The
fact of their displaying conspicuously, on signs and billheads,
“Sanitary work executed on the most scientific principles,” is not
always a guarantee that a healthy house can be received from their
hands.
In the house above referred to, everything to the eye appeared sound and
good, but on the house being occupied, a disagreeable odour was noticed
in the kitchen, and in some of the lower rooms. The sink-pipe, which was
pointed out by the builder as being “cut off,” ran from the sink trough
without a trap or water-seal of any kind, and through this pipe, when
the doors were shut, the air was supplied to the building at the rate of
180 feet per minute. The back of the W.C. was ventilated from the
outside to give free ventilation to the space under the seat, and
through the ventilators (which were working as inlets) the air came into
the house, which supplied the bedrooms, passing over the pan, between it
and the seat.
The above is an illustration of a house where the sanitary arrangements
were supposed to be on the most scientific principles! Fresh air being
supplied to bedrooms by passing over the closet-pan, and in the kitchen
and rooms below by passing through a 2-inch sink-pipe. This is one of
the many cases that may be mentioned to show the necessity of testing
any system of drainage and sanitary fittings.
This is not an unusual occurrence, as thousands of similar cases exist,
where the principal air supply passes over sanitary fittings or through
apertures which bring it in contact more or less with decomposed matter.
In a building where a number of fireplaces exist, a constant current of
air is passing in from the outside, which after mixing with the air in
the building escapes up the chimney. An ordinary chimney extracts from
the room from 60 to 120 cubic feet of air per minute, thus in a
ten-roomed house you have going out of the chimneys at least 1000 cubic
feet of air per minute. When the house is closed this large volume of
air is drawn into it through apertures offering the least resistance,
whether it be ventilators in the w.c., kitchen sinks, or drains in the
basement (which traps may have been siphoned), over sanitary pipes or
through doors and windows. Whichever point offers the least resistance,
there the supply to feed the chimneys will come.
The injurious effects on the health of persons who occupy buildings that
take in their air supply through unclean apertures are too well known to
those medical men and others who have had experience in sanitary
matters, and it can be only estimated by results. I could enumerate
cases where the health of the inmates and the death-rate were conclusive
evidence to prove the disastrous effects produced by air being supplied
through such inlets. One case in particular, which consisted of eight
blocks of buildings planned exactly alike. The drains were cut off on
the outside at the foot of all soil-pipes, and a second disconnection
about 50 feet from the building. In one building the basement was
drained into the branch drain with a trap in the inside, and from the
quantity of water and soil which flowed through this branch drain the
basement trap was constantly being siphoned, leaving a 6-inch air supply
into the building through 50 feet of drain. This, combined with 200 feet
per minute through the W.C., had the effect of causing an unusual
depression of spirits in the occupants of this building, and more deaths
occurred in this one block than in the whole of the others.
It does not require a large amount of scientific knowledge to ensure a
healthy building. What is required is sound pipes, the area of them in
proportion to the work they have to do, tight joints, and a knowledge of
ventilation. Nothing must be left to theory. A pipe either leaks and
lets out the soil, or it is sound. If it is sound, sewage matter can be
carried through it anywhere without the slightest injury to health or
unpleasantness of any kind. Pipes can be ventilated without traps being
siphoned, and the gases from sewers and soil-pipes treated so as to
ensure healthy buildings at a moderate cost.
As a rule, the first intimation of any defect in the drainage system of
a town or the sanitary fittings of a building is given by the medical
officer of health or the medical attendant of the family, whose
attention has been forcibly drawn to it by the serious illness of the
inmates.
It is no unusual occurrence, that after the medical officer, surveyor,
and inspector of nuisances have made a minute inspection of a building,
they leave it without discovering defects which exist in pipes carefully
cased over, or in the sanitary fittings.
To detect the manner in which poisons from drains are thrown into a
building and inhaled by the occupants, is oftentimes not an easy matter.
In many cases the drains have been so cut about and additions made to
them, that to trace defects or even the number of drains which are
attached to the branch drains or sewers, a considerable amount of
excavating is necessary.
The system described in these pages is intended to prevent in a measure
this excavating, and to enable a person above the ground to determine
the number, capacity, and state of the drains underneath the surface, as
well as to more readily discover any imperfections in soil-pipes and
sanitary fittings.
When sewers are laid to a town or district, it is the practice of the
authorities to let the work by tender, the lowest tender being
oftentimes accepted; consequently it is in the interest of the
contractor to get the work done as quickly and cheaply as possible.
It is impossible for the engineer, or clerk of works, to see the whole
of the work done, and the result is that a large quantity of bricks
which form the sewer are not properly bedded. Liquid sewage finds its
way through the joints of the brickwork and percolates through the soil,
in some cases to a very considerable distance, contaminating the water
it mixes with on its course, and oftentimes it forms a putrid mass under
the basement of buildings which happen to be of a lower level than the
sewers. To prevent this, a clause should be inserted in the contract
that each length of drain or sewer should be tested by atmospheric
pressure, say 5 lb. to a square inch.
The top of the sewer should be as tight as the bottom to prevent any gas
escaping through the sandy soil or rubble which may be filled in around
the sewers or drains.
Leaky sewers and badly-jointed pipes under the soil should never be
allowed, yet the danger is not so great in them as in those pipes laid
above the ground. Joints to these pipes so often leak that without
testing them thoroughly when laid, one leaky joint would cause an
unpleasant odour in a building for years without its source being
discovered. The reason of this is, that the current of air passes
through buildings in a thousand different ways. I have known a sickly
odour to come from a cupboard on the first floor of the wing of a
building some 60 feet from any soil-pipe or grating; one case in
particular, that of a nursery cupboard. This occurred through a leaky
soil-pipe from the closet in the basement of the building.
From the planning of the building the chimney near the cupboard had the
greatest draught of air in the house, and the air which supplied this
chimney came principally from the basement. The sewer gas from the leaky
joint, being of a heavier gravity than the atmosphere of the house, was
carried along the floor unobserved to this particular room, filling at
night, when the fire was not burning, this cupboard, which contained
linen, and this held the impurities given off from the leaky joint in
the pipe.
Many cases of a similar nature could be mentioned, where families will
never recover the loss sustained by them through similar leaky joints in
the soil-pipes.
Insufficient fall to sewers does not often occur in those laid under the
supervision of engineers, but it is in the branch drains connected to
them where so many blunders are made. Oftentimes one part of a drain is
laid almost level, whilst another part is laid with a steep gradient.
This facilitates the choking of drains, and the siphoning of traps.
Some persons lay drains from houses to the main sewer or to branch
drains which are altogether out of proportion to the work they have to
do.
The smaller the drain is kept the better, but the diameter should be
regulated according to the quantity of water and soil flowing into it,
taking into consideration the possibility of additional inlets being
added.
The best plan is to collect the number of inlets or supplies to the
drain, compare them with the gradient to which they are laid, and put in
a drain which, if all the inlets are supplying water at the same time,
would not fill more than nine-tenths of its area.
In some cases I have seen a 9-inch drain laid from a house having only
two closets, sink and bath outlet attached. If the whole of these were
used at the same time, the area of the flow into the drain would only be
7·696 inches, but in the 9-inch drain the area would be 63·617 inches,
or nearly nine times the size required to carry off the water and soil.
The whole space not occupied by water and soil is filled with gas, which
extracts poisons from sewage and distributes them at outlets according
to the displacement caused by the water and soil entering and flowing
through the drain.
Architects and builders laying drains to houses or buildings should
discard the theories of any persons who do not keep to this rule: that
the smaller the drain is, the better, providing it does not fill; and
the least quantity of gas there is in the drain, the less dangerous will
be the poison in the gas when discharged through openings or gratings.
The reason of this is, that in a small drain only a small quantity of
the sewage is exposed to the action of the gas in transit; whereas in a
large drain the greater portion of the sewage is exposed, thus
increasing its decomposition.
When storm water from houses or land enters drains, great care should be
taken to form openings or inlets near where drains are likely to fill,
as the injurious effects of trap siphoning are of serious consequence to
health.
In many cases the construction of new drains and sewers in a district
have been simply a waste of money as regards improving the health of the
inhabitants, and numerous cases of zymotic disease, and in some cases an
epidemic has occurred where previously such diseases were almost
unknown. This is caused principally by connecting old drains (some of
which are disused ones and connected with old cesspits) to the new
drains leading to the sewers.
In cesspits and old drains the soil and putrid matter have been for
years allowed to accumulate, and the poison from such matter, when
distributed into the open air through gratings in the new sewers or into
houses, is, when inhaled into the system, the cause of these zymotic
outbreaks. In tracing these old drains and in preventing stagnant gases
from remaining in any portion of the drain, the engineer or architect
cannot pay too much attention, as confined gases when charged with
poisons from putrid matter are the principal factors in producing
disease.
Many persons place a well-constructed trap at the inlet, and another
some distance along the drain, say at the end of a building or grounds,
without any ventilation between the two traps. In fact this used to be a
common occurrence; but it should never be done. If the drain should be a
6-inch one, and the traps 50 feet apart, the amount of gas between the
two traps would average 9 cubic feet, and this gas would in the ordinary
working of the drain remain for years, getting more poisonous the longer
it remained undisturbed. The owner of the house, knowing that he had a
good trapped drain connected to sewers, would feel himself safe, and
naturally think his house healthy. Far better for him if the house were
drained into a ventilated cesspit, as when the gases in the drain became
released, which may occur by the siphoning of the traps at the
house-connection, the danger would be equal to the emptying of a disused
cesspit, and carrying the contents through the house. The more a person
tests the working of gas in sewers or drains the more he will find that
branch drains from their construction supply the poisons which render
the gases in the sewers themselves so noxious.
In 1880, whilst engaged in tracing the course of an outbreak of typhoid,
I made a series of experiments with a view to trace the source from
which the disease emanated, and every experiment proved that the origin
of the disease lay in the gases which were in contact with putrid sewage
matter, existing in old drains and cesspits attached to the sewers as
well as in the gases which were confined between traps. The distribution
of the disease was due to the imperfect construction of the sewers,
drains, and sanitary fittings.
The most successful experiment, and the one from which the greatest
result was obtained, and which I have ever since most successfully used,
was in determining the state, size, and condition of the drains
underground, and also that of the house or buildings, by measuring by
compression the gas contained in the sewer or sanitary fittings. The
principal cause of its distribution was the compression of the gas
between the water-traps, the siphoning of house-traps leaving at times a
free passage for the gas to enter the house.
The amount of compression or displacement necessary to force the gas in
bulk through the traps has been accurately measured, to know what
quantity of liquid was required to be thrown into a drain or sewer of
any size to force the gas in bulk through the water-trap. The lifting
power of the gas on the water by compression was found to be 1/300 part
of its bulk. Thus, if a drain perfectly sound, and sealed with a
water-seal each end, held 300 feet of gas, 1 cubic foot of water thrown
into the drain would force the gas in bulk through the water-seal.
It became evident, that if both ends of any drain were sealed with a
water-trap or otherwise for testing, the capacity of the drain or leaks
of any kind could be determined without excavating.
As it was inconvenient to watch the working of the drain through the
traps, I constructed an instrument called a detector[1] to observe the
working of the atmosphere in the drain. This instrument, or a
gas-pressure gauge, when attached to the drain, will denote by the
rising of the liquid the amount of compression in the drain. This, when
compared with the quantity of water thrown into it, will give the size
and capacity of the drain, and will also indicate any siphoning of traps
or leaks which exist in any of the sanitary fittings of the house.
Footnote 1:
This instrument with instructions as to reagents can be obtained from
E. Cetti, Meteorological Instrument Maker, 36, Brooke Street, Holborn,
price 12_s._ 8_d._ It is cheaper and more convenient than the
pressure-gauge, and registers any pressure during the testing of
drains.
The following table will show the amount of gas in every 100 feet of
circular pipe or drain, from 4 to 30 inches in diameter, also the amount
of water thrown into a trap to produce the necessary pressure of gas to
lift the liquid 1 inch in the detector or pressure gauge: the quantity
being as near as possible 3⅓ ozs. of water to 1 cubic foot of gas space.
[Illustration: Plate 1.]
─────────────────┬─────────────────┬─────────────────┬─────────────────
Diameter of │Cubic Contents of│ Amount of Water │Area of Pipe 1728
Circular Pipe or │ Gas in each 100 │to produce 1 inch│ = 1 cubic foot.
Drain. │ feet length of │rise of Liquid in│
│ Drain Pipe or │ Detector. │
│ Sewer. │ │
─────────────────┼─────────────────┼─────────────────┼─────────────────
ins. │ cub. ft. │gals. pts. ozs. │
4│ 8–1255/1728│ 0 1 7│ 12·566
6│ 19–1096/1728│ 0 4 0│ 28·274
9│ 44–308/1728│ 1 1 2│ 63·617
12│ 78–932/1728│ 2 0 5│ 113·097
15│ 122–1242/1728│ 3 1 6│ 176·715
18│ 176–1234/1728│ 4 5 0│ 254·469
19│ 196–1546/1728│ 5 1 1│ 283·529
20│ 218–288/1728│ 5 5 7│ 314·160
21│ 240–913/1728│ 6 2 1│ 346·361
22│ 263–1695/1728│ 6 7 0│ 380·133
23│ 288–917/1728│ 7 4 2│ 415·476
24│ 314–276/1728│ 8 1 6│ 452·390
25│ 340–1530/1728│ 8 7 0│ 490·875
26│ 368–1212/1728│ 9 4 13│ 530·930
27│ 397–1063/1728│ 10 2 14│ 572·556
28│ 427–1147/1728│ 11 1 12│ 615·753
29│ 458–1201/1728│ 11 7 8│ 660·521
30│ 490–1512/1728│ 12 6 9│ 706·860
─────────────────┴─────────────────┴─────────────────┴─────────────────
The method of testing drains and fittings by compression of gas is as
follows:—When the drainage plan of a building exists, the work of
testing by compression of gas in the drain will be a very simple matter.
Plate 1 shows the drains as laid to a semidetached villa, with two
inlets from sinks marked 1, one from bath overflow marked 2, and two
from the soil-pipes of closets in the basement and first-floor marked 3.
The drain from A to B is a 6-inch stoneware pipe, and its length is 100
feet. The amount of gas in it would be 19–1096/1728 cubic feet. The
branch drains from the other inlets are 4 inches in diameter, and the
collected lengths are 50 feet, and the quantity of gas in them would be
4–627/1728 cubic feet, giving a total in the whole of the drain of
nearly 24 cubic feet.
If the indiarubber pipe to the detector or pressure gauge is placed in
either of the traps marked 1, and the glass tube filled with liquid up
to the data line, 5 pints of water poured into either of the traps
marked 1, will produce a rise of 1 inch in the liquid of the detector,
that is if all the drains are clear and joints tight, the drains being
stopped off for testing at A.
Should a trap be fixed anywhere between A and B a lesser quantity will
be required to lift the liquid, and the position of the trap can be
determined by comparing the exact quantity of water used with the
capacity or quantity of gas in the drain.
If a trap should be fixed or a stoppage formed in any part of the drain
A B, the flushing of a closet or sink would, by the compression of the
gas, force it in bulk through the weakest trap, or the one having the
least dip or seal. The quantity which would pass through would depend on
the amount of water used in the flushing and the fall of the drain.
The drains to the building having been tested, and their defects
ascertained, it will be necessary now to test the soil-pipe.
On this plan it is fixed on the outside of the house, having a trap with
an open grating just beyond the basement closet, and a ventilating pipe
carried above the eaves of the roof. Whether the soil-pipe be fixed
inside or outside of the building it should be perfectly gas-tight, and
in this testing a person cannot be too particular.
In testing the soil-pipe shown on plan, the easiest method is to put the
detector or pressure-gauge at the grating of the trap 3, placing the
indiarubber tube over the grating, and making a tight joint with clay.
Then close the top of the ventilating pipe and pour water in the top
closet, when, if the joints are tight, the liquid in the detector will
rise suddenly, and then lower itself as the water leaves the trap,
indicating that the soil-pipe is tight, but if it is not tight, no
rising of the liquid will take place. Should there be no trap at the
bottom of the soil-pipe, it will be necessary to excavate down to the
drain to take out a length of pipe, to seal the mouth of the drain with
clay for testing. If there should be leaky joints or holes in the
soil-pipe, a little sulphur burnt in the pipe, or a little pungent
essence thrown into it, will clearly denote where the leaks are.
Having tested the soil-pipe and proved it tight, or effectually stopped
all leaks as the case may be, no gas can be given off in these drains or
fittings except through the ventilators (under ordinary circumstances)
as no trap has been siphoned in the testing.
As before stated, the ventilating pipe runs to the top of the building
of the same diameter as the soil-pipe, in fact this is a plan of drains
to a house recently built in the suburbs of London, and the planning of
them would be considered perfect by many sanitary men, but before we
testify them as perfect, let us carefully analyse the working of the
ventilation.
The ventilating pipe being carried above the roof is strictly in
accordance with the bye-laws of the Local Board, although it spoils the
appearance of the house. One reason why it was put there is to prevent
the siphoning of the closet trap, and its height is to carry out the
recommendations of medical writers in the _Lancet_ who have so often
insisted that these tall pipes, carried some feet away from chimneys or
bedroom windows, were necessary.
Let us test this theory.
We will flush the closet by throwing down slops and giving the closet
the regular flush, carefully testing what takes place. The result is
that the soil-pipe, instead of carrying off the odours from the top,
only forms an air inlet, and 2¼ cubic feet of air has been sucked in at
the top of the pipe, and the same quantity of gas discharged through the
grating. As this grating on the plan is only 2 feet from the passage
door which leads into the kitchen, the least that occurs is that a
portion enters the house, and the cook has a slight headache when
preparing the meals for the day.
To be more certain of this let us test the working of the ventilation by
a dozen flushings of the closets, and the same results are obtained by
measurement, 27 cubic feet of air entered the top of the pipe, and has
been driven out at the grating below. This proves that it is unnecessary
to spoil the appearance of our houses by the erection of these pipes, or
of carrying them above the soil-pipe or closet level.
It would not be consistent for me here to state how these unsightly
pipes could be avoided, but I am confident that ere long they will
become obsolete, although they have been erected by thousands in various
parts of the country.
We will now test the working of the ventilation in drains A B, and those
in branch drains to traps marked I. As they are clear, we find that the
gases in them are not so poisonous as in the sewers to which they are
connected.
A manhole grating exists in the sewer some 40 yards from the back of the
building, and through this grating the gas which is driven by the
flushing escapes, and its density depends on the nature of the soil
passing in the sewer. Its density is lessened by diffusion, or the
mixing of the gas which takes place at the grating, but the time it
takes for the gas which is in the drain near the traps I, to mix with
the fresh air at the grating in the street is a problem that I will
leave others to solve. We are certain that no gas in bulk can pass
through the trap under ordinary circumstances.
We can now certify that the drains are tight, well trapped and
ventilated, they are laid strictly in accordance with the bye-laws of
the Local Board, and we can quote that similar plans were exhibited last
year at the Health Exhibition, as models for country architects and
builders to copy; and ninety-nine out of every hundred sanitary
inspectors would sign the certificate that the sanitary arrangements
were carefully tested, and found perfect.
[Illustration: Plate 2.]
Experience in working the detector will not allow me to do this.
Although for months not the slightest particle of sewer gas has entered
the building, until one evening about eight o’clock a sickly smell is
observed in the kitchen, and this is attributed to a change in the
weather, heavy rain having fallen during the day, and no notice was
taken of it before retiring to rest. In the morning the house is
unbearable. The inspector of nuisances is sent for, who cannot detect
anything wrong in the drains. The surveyor to the Local Board visits the
house with the same result, and it is not until the middle of the day
before the nuisance has abated, its cause still a mystery to the
sanitary officials and to the owner of the house, who is a medical man
of great experience in sanitary matters, and a sanitary writer.
Now what really did occur was this. The sewer at the back nearly filled
with water and soil caused by the heavy rains, and when this was rising,
about 2 cubic feet of gas was forced from the drain B through the
grating at the bottom of the soil-pipe. The junction where the drain at
A joined the sewer was made as usual about two-thirds the height of the
sewer, consequently the drain from A to B filled some 20 feet during the
storm. When the storm abated, the water leaving the drain at A sucked
the trap at the bottom of the soil-pipe 3. The seal being gone, the gas
from the sewer at once came through the trap, the current being
estimated at from 80 to 200 feet per minute; so that the quantity of gas
given off at the trap, which is 2 feet from the door, would be about
2000 cubic feet from the time the trap was sucked until it was filled
again by the flushing of the closet.
This is by no means an exceptional occurrence, two similar cases
occurred in the suburbs last year. In one case the owner of the house
was seriously ill for several days, and was for some weeks obliged to
neglect his business and seek a change of air. In the other case the
daughter was taken ill with a zymotic disease which nearly cost her her
life, and it was months before she regained her strength.
The easiest method of preventing this siphoning of the traps is to fix a
small mica valve at the most convenient part of the drain between A and
B, fixing it above the ground. You can also prevent it as well as the
gas coming near the house by putting in a trap at A and having an open
grating between A and B. This would not prevent the 2000 cubic feet of
gas before referred to from escaping from the drains, but would cause it
to be discharged some distance from the house. You would also have about
23 cubic feet of gas in the drain always mixing with the atmosphere of
the garden at this point when the traps are full and tight.
Plate 2 shows the plan and drains of a hospital which I tested by this
system in 1880. As it was an old building the testing was somewhat
different to that described in Plate 1.
[Illustration: Plate 3.]
For years a sickly smell was observed in the ward, and more especially
when the heating apparatus was at work, and it was thought to arise from
the number of bad cases in the ward. A good system of ventilation was
adopted by the introduction of fresh air through flues which ran under
the floor to the whole length of the building, and in winter the air was
warmed by passing over hot-water pipes in the flues, and was distributed
at various parts of the ward through open gratings in the floor, with a
good extraction in the roof, which was open to the ward, but ceiled over
the rafters.
Double the amount of fresh air was admitted, warmed, and extracted, with
a view to improve the atmosphere of the building, but with no better
results. I then decided to test the drains which were shown on the plan
of the building as on Plate 2, the drain marked A B being tested first
by stopping it off and fixing the detector at B. This being a 9-inch
drain pipe and the length 130 feet, gave 57–600/1728 cubic feet as the
contents of gas in it. Adding 6 cubic feet for the branch drain at C,
making a total of 63–600/1728 cubic feet.
The amount of water required to be thrown into the trap A would be 1
gal. 5 pts. 3 ozs. to produce the necessary pressure of gas in the drain
to lift the liquid 1 inch in the detector. Instead of taking 1 gal. 5
pts. 3 ozs., it took 7 gals. 6 pts. 9 ozs., giving an additional 237
cubic feet of gas space to be somewhere attached to the drain. This
could not be leaks, if it had been the liquid in the detector would not
have risen at all.
The ground was opened at D, the drain sealed, and the detector fixed,
and the total quantity of gas in the drain by measurement from the seal
to trap A was found to be 46 cubic feet, and by testing this was found
to be correct, consequently the additional gas space was between B and
D.
I particularly noticed that the gases in these drains were more
poisonous than they should have been, considering the nature of the
sewage flowing through them, and by using a reagent as a liquid in the
detector, its discoloration indicated that the gas was in contact with a
large quantity of putrid matter which was of a different character to
that of the sewage flowing in the drain.
A drain searcher, or pointed rod was used, and after driving it into the
ground a few times, it struck the large cesspit E, and by the sound
given it was clear that a drain was underneath, when, on excavating, the
old cesspit and drains shown on Plate 3 were discovered, containing more
than 60 cubic yards of black putrid sewage.
The junction at F was cut off and the drain made good, when a second
testing by fixing the detector at B gave the quantity of gas in the
drain to be 63–600/1728 cubic feet.
The cleaning out of 60 cubic yards of sewage and the removal of the old
drains did not in the slightest degree diminish the nuisance inside the
building, consequently the 15-inch drain on the opposite side of the
building was stopped off at G and H, and in testing the detector was
placed at G. This length of drain being 140 feet contained 175–1098/1728
cubic feet of gas, and 4 gals. 4 pts. 8 ozs. of water thrown into the
trap H should have lifted the liquid to the usual height in the
detector. This and a similar quantity of water did not indicate any
compression, but the discoloration of the reagent in the detector was
much quicker than on the drain which was first tested.
The drain was then opened at I, dividing it into two sections, that from
G to I containing 93 cubic feet. Testing this by 2 gals. 3 pts. 6 ozs.
of water gave the exact rise in the detector, consequently the leaks and
bad gas must be in the section from I to H. This was tested by a fresh
reagent in the detector, when the speedy discoloration of the liquid
indicated that the source of the poison was very near.
By a few piercings of the ground at K, by the iron rod or searcher, the
drain was found, and by following the old drain the two cesspits and
additional drains shown in Plate 3 were discovered, and about 150 loads
of old putrid sewage had to be excavated and cleared away. The leaks
which prevented the rise of the liquid in the detector were in the crown
of the old sewage tank M, and the hot-water pipes of the heating
apparatus running in an air-shaft just over it, the heat extracted the
poisons from the sewage and distributed them into the ward.
The connections at K and N having been stopped up, the drain from I H
was again tested, when it gave 36 cubic feet more gas space than there
should have been in the drain. A few piercings of the soil at O led to
the excavating of those old drains which are shown attached, and these
being excavated and cleared away, and the connections to drains K, N,
and O being stopped, the drain was again tested from I to H, when
compression in the detector took place in comparison to the exact
quantity of gas that should be by measurement in the drain.
In describing the method of testing drains as shown on Plates 1, 2, and
3, nothing has been mentioned as to the level to which branch drains to
houses should be laid, or the method of testing them to ascertain their
fall.
The fall given to branch drains should not be less than 1 in 100, but 1
in 80 is far preferable, and if the drains are laid to this level, water
will flow easily through them, but should any part be laid out of a
level the water would lay in them and thus give a less quantity of gas.
Then when tested by compression to the capacity of the drain the lesser
quantity would denote the nature of the dip.
When a plan of drains exists, as in the two cases shown on Plates 1, 2,
and 3, the difficulty of testing them and proving their defects will not
be as great as when no plan has been made. If no plan has been made or
no record kept of them, it is best to make a rough plan of the building,
fixing the positions of all inlets, their sizes and lengths, of branches
to the drains on the premises, and also to lay down on the plan the
length and size of this drain to where it reaches the extent of the
property or joins the main sewer, opening the ground for testing in a
similar manner to that described in Plate 1.
In testing pipes or sanitary fittings of any kind, leaks can be easily
found by attaching the detector or pressure gauge to the most convenient
part of the pipe or fitting, and when everything is sound care should be
taken to flush all inlets at the same time, to ascertain whether the
rush of water has any effect on the traps or water-seal. If the
vibration in the detector or pressure gauge exceeds 2/10ths of an inch,
a freer gas space must be provided, or the action of the water checked
in some manner. Pipes, whether sanitary or otherwise, can be tested as
to tightness in a similar manner.
Some modification may be necessary in testing large sewers or the drains
of a district, but if the testing is performed in a similar manner to
that adopted in the above case the condition of the drains and fittings
can be accurately ascertained. The least pressure or suction on the
traps of drains or fittings will be shown by the vibration of the liquid
in the detector or pressure gauge when the water passes through the
pipes with flushing.
The term “bad drains” is not exclusively confined to those drains that
have leaky joints, or have an insufficient fall, or traps which siphon
during the passage of the water, but may also be applied to systems of
sewers in general. There are two points in almost every system of
drainage that call for some improvement. The first is having the inlets
at junctions where small drains join sewers at the side of the sewers.
Thousands of traps are being continually siphoned by this cause as soon
as the water fills the sewer above the inlet of the branch drain, as
this, when filled with water only a short distance, forces gas through
the weakest trap, and on the water and soil lowering itself in the
sewer, this water acts exactly as the plunger of a pump and draws the
water out of the weakest trap. This is often the one in the area or
basement of the building, and to avoid this all inlets at junctions
should enter the top of the sewers, not for the soil to drop down so as
to cause the sewers to silt, but in an oblique direction with the sewage
flow. The second point is in the ventilation of sewers, which is not an
easy subject to handle.
SEWER VENTILATION.
The question of ventilation is a very difficult one, whether it is in
connection with sewers or buildings.
The ventilation of buildings has received more attention than that of
sewers, excepting within the last three years.
In the ventilation of buildings we have the work and experience of Mr.
Haden, Captain Galton, Dr. Parkes, Messrs. Howarth, Tobin, Boyle,
Banner, and others, who have not only made the ventilation of buildings
their principal study, but have also spent large sums of money in
carrying out experiments with a view of getting a system of ventilation
applicable to any building. I have no doubt that each of the above
authorities in house ventilation would candidly admit that some of the
most favourable experiments they had made, and from which at the time
they expected the greatest results, had, when they had been practically
applied in different localities and under different circumstances,
proved their worst failures in providing a regular supply of fresh air
to and the extraction of foul air from any building.
If in the ventilation of buildings so many failures to get a perfect and
universal system can be recorded, it is quite natural that the same will
be the case in the ventilation of sewers.
The most eminent engineers of the present day will admit that vast
improvements must be made in sewer ventilation before they can say of a
district where a quantity of drains are laid and a large bulk of sewage
matter is carried through them, that the atmosphere of that district is
as pure as that of one where no drains are laid or where no sewage
matter can be found.
It was not until 1840 that the question of sewer ventilation received
very much attention, and it is in the reports to the City Commissioners
of Sewers and to the Metropolitan Board of Works that the earliest
results are recorded.
The report of Colonel Hayward to the City Commissioners of Sewers, dated
18th March, 1858, contains some of the earliest and most valuable
information as to sewer ventilation.
In that report it is stated that, previous to 1830, “the sewers were
ventilated by the gulleys, which were large open shafts or shoots
connected with the sewers without traps of any description: they were
connected with gratings of large size, the bars of which were farther
apart than those at present in use; there were no ventilating shafts
rising to the centre of carriageways, nor were there any side entrances
by which access to the sewers could be had. Whatever ventilation took
place therefore was effected by the gulleys, and if a sewer required to
be cleansed or examined the mode adopted was to open holes in the centre
of carriageways down to what are technically called manholes, or working
shafts, and perform these operations from these apertures, the shafts
being left open a sufficient length of time to ensure ventilation before
the men descended, and if there was fear of an accumulation of gas or
mephitic vapour, which sometimes was the case near the heads of sewers,
but at few other points in them.”
Complaints of the effluvium from these gulleys were made before the year
1830, and are stated to have grown louder and stronger after that date.
Here we have the first experience and results of free and open
ventilation to sewers. As regards the number of these gulleys in
proportion to the sewers we have no evidence in these reports, but
judging from their being specified as large open shafts, the area for
the inlet and outlet of air to the sewers would be if anything greater
than that of the present day. Yet this report states that the ill odours
which escaped from the gulleys, although they might not be pestilential,
became more repulsively offensive, and the attention of the
Commissioners of Sewers was drawn to the evil, and it was felt that some
remedy or palliative ought to be devised.
The means taken to obviate this evil may be termed the first experiment
in sewer ventilation.
“A gulley trap was devised and fixed in the Pavement, Finsbury, in 1834,
and in 1840 nine hundred of the gulleys had been trapped with a view to
remedy the evil, with the following results.
“It became apparent even before that number was fixed, that the sewers
were becoming dangerous to workmen to enter, and the gases generated
found vent by the house drains (then generally untrapped) into
dwellings.”
[It is quite evident that the compression of gases which takes place in
the sewers by the rising and falling of the liquid and sewage flowing in
them was not then known, or this experiment by closing the gulleys and
ventilating the sewers through the house traps would not have been
attempted.
At any rate the first experiment in sewer ventilation in the City cannot
be said to have been a successful one, as it left matters worse than
before.]
“To obviate this, ventilating shafts connecting directly with small iron
gratings in the centre of the carriageways were formed: this mode of
ventilating was also first adopted in the City, and the system of
trapping (with numerous modifications in manner) and ventilating the
sewers in the centre of the carriageways spread through the length of
the metropolis.”
Can it be said that this alteration was an improvement in sewer
ventilation?