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Objections to Sewers.
The main objections are as follows :
1. That as underground channels, connecting houses, they allow transference of effluvia from place to place. The objection is based on good evidence, but it must be said in reply that, if proper traps are put down, and if air-disconnection, in addition, is made between the outside drains and the house pipe, such transference is impossible. The objection is really against an error of construction, and not against the plan as properly carried out. Besides, the objection is equally good against any kind of sewer, and yet such underground conduits are indispensable.
2. That the pipes break and contaminate the ground.—This is a great evil, and it requires care to avoid it. But such strong pipes are now made, that if builders would be more careful to make a good bed, and to connect the joints firmly, there would be little danger of leakage, as far as the pipe drains are concerned, and not much damage of the main brick sewers. All pipes, however, ought to be actually and carefully tested after being laid and before being covered in, otherwise it is impossible to ensure their being water-tight, even when everything is sound to all appearance.
3. That the water supply is constantly in danger of contamination.—This also is true, and as long as overflow pipes from cisterns are carried into sewers, and builders will not take care to make a complete separation between water pipes and refuse pipes, there is a source of danger. But this is again clearly an error in constructive detail, and is no argument against a proper arrangement.
ON THE INFLUENCE THE CONSTRUCTION OF SEWERS HAS HAD ON THE DEATH RATE
Reference has already been made to the possibility of sewers being the channels by which enteric fevers and cholera have been propagated from house to house, and from which emanations, causing diarrhoea and other complaints, may arise. Admitting the occasional occurrence of such cases, it remains to be seen whether the sanitary advantages of sewers may not greatly counterbalance their defects. The difficulty of proving this point statistically consists in the number of other conditions affecting the health of a town in addition to those of sewerage. Dr. Buchanan' has, however, given some valuable evidence on this point, which has been well commented on by Mr. Simon. He inquired into the total death rate from all causes, and the death rate from some particular diseases, in twentyfive towns before and after sanitary improvements, which consisted principally of better water supply, sewerage, and town conservancy. eral result is to show that these sanitary improvements have resulted in a lowering of the death rate in nineteen out of twenty-five towns, the average reduction in these nineteen cases being 10.5 per cent. The reduction in typhoid (enteric) fever was extremely marked, and occurred in twenty-one towns out of twenty-four, the average reduction being 45.4 per cent. in the deaths from typhoid. In three cases there was an augmentation of typhoid fever, but this was manifestly owing to imperfection in the Sewerage arrangements ; and these cases afford excellent instances of the
Ninth Report of the Medical Officer to the Privy Council, p. 12 et seq. and
unfavorable part badly arranged sewers may play in this direction.' Soyka ' has given some interesting statistics of German towns with regard to this point. In Hamburg the typhoid deaths per 1,000 total deaths has fallen from 48.5 to 10.5; in Dantzig, from 26.6 to 2.3. In Frankfort the typhoid deaths per 10,000 living have fallen from 9 to 2; in Munich, from 24.2 to 8.9
Diarrhæa has also been reduced, but not to such an extent; and in some towns it has increased, while typhoid fever has simultaneously diminished.' But the term diarrhæa is so loosely used in the returns as to make any deduction uncertain. Cholera epidemics Dr. Buchanan considers to have been rendered - ‘practically harmless." The immense significance of this statement will be at once appreciated. Whether the result is owing solely to the sewerage or to the improved water supply, which is generally obtained at the same time, is not certain. Phthisis, which Dr. Buchanan and Dr. Bowditch * find to be so much influenced by dampness of soil, does not appear to have been affected by the removal of excreta per se, at least towns such as Alnwick and Beynmawr, which are thoroughly drained, show no lowering in the phthisical mortality. Nor could Dr. Buchanan trace any effect on the other diseases of the lungs.
As far as can be seen, the effect of good sewerage has therefore been to reduce the general death rate, especially by the reduction of deaths from typhoid and from cholera (and in some towns from diarrhea), but partly, in all probability, by general improvement of the health. The action has been, in fact, very much in the direction we might have anticipated.
It may be observed, that this inquiry by Dr. Buchanan does not deal with the question as between sewers and efficient dry methods of removing excreta (on which point we possess at present no evidence), but between sewerage and the old system of cesspools.
MODIFICATIONS OF THE WET METHOD OF REMOVING EXCRETA.
The Separate System. By this term is meant the arrangement which carries the rain water in separate channels into the most convenient water-course." Mr. Ward's celebrated phrase "the rain to the river, the sewage to the soil," is the principle of this plan. Its advantages are that the sewers can be smaller ; that the amount of sewer water to be dealt with at the outflow is much less in quantity, more regular in flow, and richer in fertilizing ingredients, and is, therefore, more easily and cheaply disposed of. The grit and débris of the roads also are not carried into the sewers; and the storm waters never flood the houses in the low parts of the town.
The disadvantages are, that separate channels and pipes have to be provided for the rain ; that the rain from all large cities carries from roofs and from streets much organic débris which pollutes streams, and that the
See the case of Worthing (p. 45, Ninth Report, etc., op. cit.), for a striking instance of the spread of typhoid through sewers.
2 Deutsche Viertelj. für Off. Ges., Band xiv., Heft 1, 1882, p. 33.
See especially Dr. Buchanan's Report in the last-named work, p. 57.
On this subject the works of Mr. Menzies, who first described this plan, and of Colonel Ewart, R.E. (Report on the Drainage of Oxford, Eton, Windsor, and Abingdon, 1868), will be found very useful.
scouring effect of the rain on sewers is lost, though this last is a very questionable objection.
The adoption of one or other system will probably depend on local conditions. If a town in Europe lies low, and it is expensive to lift sewage; if land cannot be obtained; or if the natural contour of the ground is very
favorable for the flow of rain one direction, while it is convenient to carry
sewage in another, the separate system would be the best. So also in the tropics, with a heavy rainfall and a long dry season, the providing of sewers large enough to carry off the rain would be too expensive for all except the richest cities, and the disposal of the storm water would be difficult.
In all cases in which rain enters the sewers, some plan ought to be adopted for storm waters.' If irrigation is the plan carried out, the sewer water becomes so dilute and so large in quantity in storms, that the application to land is usually suspended, and the sewer water is allowed to pass at once into streams.
In this way the evil which irrigation is intended to prevent is produced, though, doubtless, the sewer water is highly dilute. In London, the storm waters mingled with sewage are allowed to flow into the Thames, special openings being provided.
The Interception System. In many of the continental cities the fluid and solid excreta fall into a receptacle with perforated sides or bottom, so that the fluid part drains away and the solid is retained, and is removed from time to time. Such a plan may keep the sewers free from deposit, but has the great disadvantage of retaining large collections of excreta close to and in many cases immediately under or in the cellars of houses, and no ventilation can entirely remove all effluvia.
An improvement on this plan is a method proposed by Mr. Chesshire, of Birmingham. He places outside the house, in any place where access is easy, a comparatively small box, connected by trapped pipes with the water-closet at one end, and the sewer at the other. The lid of the box is fixed down with concrete or putty, so that the access of air is stopped. Across one end of the box is a single or double strainer, which allows the urine and water to pass, but retains the solids. From time to time the box is lifted out, carted away, and another is inserted. The solid matter is almost free from odor, as the limited access of air hinders putrefaction..
The difficulty about this plan is the occasional blockage of the strainer, so that the solid matters remain wet, and may soon fill the box, so that the lid may be forced off. The liquid which flows from the box is of course highly impure with excreta, but the retention of the solids prevents blockage of the sewers. At present it can only be said that this plan has not been yet practically established on the large scale, but is well worthy of extended trial, particularly in cases where the difficulties of irrigation are great.
Water-Closets and Water-Troughs. Water-Closets.—The pan of the closet is usually a cone in earthenware (which is better than metal), and a siphon or flap valve below. In addition, there are numerous contrivances for flushing the pan and siphon,
Plans for this purpose are figured and described in the works on Sanitary Engineering, by Baldwin Latham and Bailey Denton.
and for preventing the escape of the air from the soil pipe into the house.” The soil pipe is usually of cast lead ; but both lead and iron are easily eaten through, as shown by Drs. Fergus and N. Carmichael, and earthenware pipes, if strong and well joined, would be preferable.'
The points to be looked to in examining closets are—1st, that the pan is nearly a cone, and no a half circle with a flat bottom; 2d, that the amount and force of water is sufficient to sweep everything out of the siphon ; 3d, that the soil pipe is ventilated beyond the siphon, by being carried up full-bore to the top of the house ; 4th, that the junction of siphon and soil pipe and the lengths of the soil pipe are perfect.
With respect to water, a pipe from the house cistern frequently leads to the closet; but if so, there is danger of gas rising through the pipe. There should be a special small cistern for the use of the closet.
What are termed water-waste preventers are now commonly used, fed either by a cistern or by constant supply. They are boxes which are emptied by a valve into the pan, and are then refilled. There are many kinds, but perhaps the best are those that work by siphon action, brought into play by pulling a wire. The amount of water should not be less than two gallons, and the fall should not be less than 3 or 4 feet, so as to insure thorough scouring of the soil pipe."
The ventilation of the soil pipe is a matter of importance, as the water from the pan suddenly displaces a large body of foul air, which rises through the siphon as the water flows. The best plan is to carry up the soil pipe full-bore to the roof, far from any windows. It is well also to have a second pipe from the crown of the siphon to the ventilating pipe, in order to prevent the unsiphoning of the trap (see Fig. 84). Air is supplied by a grating below, as in Buchan's and other disconnecting traps, or (as in Banner's plan) by drawing air from another shaft carried up the house. The currents in the two shafts are determined by reversed cowls. In some cases it is proposed to draw the air down the soil pipe and up another pipe.
The simple hopper closet, or some form of “wash-out” closet, with a siphon trap below, is the safest ; but there are some good forms of valve closet in the market. They are, however, too frequently made with overflow pipes passing into the soil pipe. These, although siphon trapped, are apt to be sucked dry. They are thus dangerous, and they are really unnecessary, for a well-made siphon pan rarely overflows. If it does, it is better to receive the overflow on to a safe under the closet, from which the water flows out through a pipe to the open air, such pipe acting as a warning pipe. The old pan-closet, with its filthy container and D trap, ought to be absolutely discarded.
The position of the closet is a matter of great moment. If possible, it should always be in an outbuilding, or a projection, with thorough ventilation between it and the house. In two-storied buildings it might be put in a small third story in the roof, and well ventilated above. The windows in a closet ought always to open quite to the ceiling.
* Mr. Eassie's work, Healthy Houses, gives a good account of the various kinds of closets.
* In his work on Sanitary Arrangements for Dwellings, Mr. Eassie does not approve of earthenware pipes, preferring the strongest cast lead to any other.
• The Army Sanitary Committee (On Sanitary Appliances, Blue Book, 1871, p. 17) state that the amount of water used in the water-closets in the army is, for Green's closet, between $ gallon and 1 gallon for each time of use; Underhay's, Lambert's, and the pan-closet, from 1 to 17 gallon; and for Jenning's closet, usually the same, or in some stations 3 gallons.
In all cases, a tube should pass from the top of the closet to the outer air, and, if the closet is in a bad situation, the tube should be heated by a gas-jet.
It is a bad plan to have the pull-up handle covered by the lid ;' it should be able to be pulled up when the lid is shut, or the shutting of the lid should open the water-waste preventer cistern. In wash-out closets the flush is often obtained by pulling a wire like a bell-pull, as mentioned above.
The plan of placing closets in the basement should be entirely given up; closet air is certain to be drawn into the house.
Water-Troughs or Latrines.—These are very strong earthenware or castiron receptacles, which are about half full of water. The excreta drop into the water, and once or twice a day a valve is raised, and the water and excreta pass into a drain. There is usually a receptacle into which fall bits of bricks, towels, or other things which are thrown in, so that they are stopped and fished out when the trough is emptied, and do not pass into the drain. The amount of water in the water-latrines used in some barracks is about 5 gallons per head daily, so that the plan is not economical of water, but, as it avoids all loss by the dripping in closets, there is probably no great excess of expenditure. It is a good plan to have a flexible hose attached to the water pipe, so as to wash thoroughly the seats and partitions every day.
The chief objection to this plan has been the labor which is necessary to empty the trough ; but this may be obviated by the use of automatic flush tanks, discharging periodically. On the other hand, there is saving of expenditure in repairs to water-closets.
In judging of the value of a water-trough, the amount of water, the surface exposed to evaporation, and the completeness of the flushing, are the points to look to.
DRY METHODS. The use of sewers and removal by water are in many cases impracticable. A fall cannot be obtained ; or there is insufficient water ; or the severity of the climate freezes the water for months in the year, and removal by its means cannot be attempted. Then either the excreta will accumulate about houses, or must be removed in substance daily or periodically. Even when water is abundant, and sewers can be made, many agriculturists are in favor of the dry system, as giving a more valuable fertilizing product; and various plans are in use.
It is not necessary to consider here the employment of cesspools, dead
'In Dr. Aldridge's patent the handle cannot be pulled up until the lid is shut down ; there is also arrangement for carrying off foul gas by means of a pipe communicating with the outer air, the lid itself being air-tight round the rim of the seat.
In the army two kinds of latrines (Macfarlane's, of cast-iron, and Jenning's, of Earthenware) have been in use for about twenty years. The Army Sanitary Committee (On Sanitary Appliances introduced into Barracks, Blue Book, 1871, p. 14) state that out of 183 barracks only 53 have been charged with repairs, and the average expenditure on these 53 has been 12s. per barrack annually for Macfarlane's, and 18s. 9d. per barrack for Jenning's latrine, and nearly the whole of these expenses have been caused by articles thrown carelessly into the latrines.
On the dry methods of removal a very good paper has been published by Dr. Buchanan and Mr. Radcliffe (Twelfth Report of the Medical Officer to the Privy Council
, 1870, pp. 80 and 111); also another by Mr. Netten Radcliffe (Report on certain Means of preventing Excrement Nuisances in Towns and Villages, New Series, No. 2,