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The water-carriage system of sewerage will be noticed here under its three aspects:–(1) the ultimate disposal of sewage; (2) the system of common sewers by which sewage is conveyed to its destination; (3) the domestic arrangements for the collection of sewage. I. THE ULTIMATE DISPOSAL of WATER-CARRIED SEWAGE.-In the water-carriage system of sewerage the fertilizing elements are so largely diluted that it becomes a matter of the utmost difficulty to turn them to profitable account. It has been estimated that every ton of London sewage contains ingredients whose value as manure is rather more than 2d.," a value which, could it be realized, would make the sewage of the metropolis worth a million and three quarters sterling per annum. Sewage farming, however, does not pay. After much costly experiment the conviction is gaining ground that, neither by applying sewage directly to land, nor by any process of chemical treatment that has yet been proposed, can sewage be made to yield a return as manure which will cover the cost of its transport, treatment, and distribution, except perhaps in a few cases where the circumstances are peculiarly favourable. At the same time, sewage farming does afford one satisfactory solution of the problem of how to dispose of sewage without creating a nuisance—a problem in which any question of profit or loss is of secondary importance. A very early instance of irrigation by sewage is that of the Craigentinny Meadows, a sandy tract of 400 acres, or which part of the sewage of Edinburgh has been discharged during certain seasons for nearly a century. There, owing to favourable conditions, and to the fact that complete purification of the sewage is not attempted, the process yields a profit; but no such result could be looked for if the sea were not at hand to receive the imperfectly cleansed sewage and the wholly uncleansed surplus. Germany furnishes a still older example of irrigation in the sewage farm of the town of Bunzlau, which has been in existence for more than three hundred years. Five methods of treating sewage may be named, of which two or more are often found in combination. JDischarge into the Sea or into a large watercourse is in general the least costly means by which a community can rid itself of its sewage. , j care in the choice of outlets is necessary to make this plan effective in avoiding nuisance. Some towns mako use of tanks or outlet-sewers of large capacity, from which the discharge is allowed to occur only when the tide is ebbing. When the volume of sewage is very large, even this precaution does not wholly protect the neighbouring coast from foul deposits. A striking instance is furnished by the case of London, which discharges its sewage into the tidal estuary of the Thames at Barking and Crossness during only some three or four hours from the time of each high tide. It is found that the discharged matter is washed up and own the river with every tide, occasionally reaching as far up as Teddington, and that the portion which is not deposited in the form of mud banks only very slowly works its way to the sea. JBroad Irrigation.—By this is meant the use of sewage to irrigate a comparatively large tract of cultivated land, in the proportion of about 1 acre (or more) of land to every 120 persons in the sewageontributing population. This system is now largely and successully used, especially where the soil is a porous sandy loam. Fears hat the farms would prove dangerous to the health of the neighbour. ing district, and that the crops and vegetables grown on them ould be unwholesome, have proved groundless. When the farm is properly laid out and ... managed the effluent water is pure enough to be admitted to a clear stream from which water-supply is drawn. Broad irrigation is practised at Croydon, Cheltenham, Blackburn, and many other English towns; and it has recently been applicd, on a very large scale, to dispose of the sewage of Berlin. ntermittent Downward Filtration.—This is another mode of purifying sewage by applying it to land, which differs from broad irrigation in requiring a much smaller area in proportion to the sewage dealt with. In 1870 Dr Frankland 2 drew attention to the fact that if sewage were passed through porous soil, not continuously but at intervals long enough to let the soil become aerated, rapid purification took place through the oxidizing action of the
* Hoffmann and Witt, Report to the Government IR&ferees on Metropolitan Drainage, 1857. w * Report of the Jrivers Pollution Commissioners, 1870.
pany at Aylesbury, differs from others in produci
air which the soil held in its pores. . He estimated that an acre of suitable ground, well furnished with subsoil drains to remove the water after percolation, could in this way take the sewage of 2000 persons. This estimate is now considered excessive, and 1000 persons to the acre is a more recent limit. Mr J. BaileyDenton, at once took up Dr Frankland's suggestion, and in his hands the system of intermittent filtration through land has been successfully applied to the scwage of many towns.” The land which constitutes the filter is used to grow vegetables and other crops. Clay soils are, as far as possible, avoided, and the land is thoroughly underdrained at a depth of about 6 feet. The sewage is distributed over the surface in open channels, the proper laying out of which is an important item in the cost of the system, but is essential to its success. When the number of persons exceeds 500 per acre it is advisable to precipitate the solid matter that is held in sus: pension before the liquid is applied to the land, in order to prevent the surface of the ground from becoming clogged with sludge. Mr Bailey-Denton has pointed out the advantage which the system of intermittent filtration offers as a supplement to broad irrigation, where that is carried out. A serious objection to the disposal of sewage by irrigation is the fact that the farmer must take the sewage always, -at times when it hurts the land as well as at times when the land wants it. But by laying out a portion of the land as a filter bed the sewage may be thrown on that whenever its resence on the remainder would do harm rather than good. Mr enton has applied this combined system in several instances, and insists, apparently with much reason, that such a combination offers a better prospect of profit than any other efficient mode of Fo sewage. The system of intermittent filtration through and has been recommended by the Royal Commission of 1882–84 as a mode of treating London sewage. -- . . . Filtration through Artificial Filters of sand, gravel, ashes, char. coal, coke, peat, &c., though often experimented on, can scarcely be described as an actual system. It is attended by the difficulty.that the filter becomes speedily choked by the deposit of sludge. The intermittent use of a suitable artificial filter will, however, serve efficiently to oxidize and therefore purify the o portion of sewage from which the sludge has been previously precipitated, and filtration through coke is used in some instances as a supplement to the process which is next to be described. Chemical Treatment, or Precipitation.—When sewage is allowed to stand, or to flow very slowly through a large tank, a gradual subsidence of the solid particles takes place. The subsidence is, however, much too slow to be complete before decomposition sets in. But it may be very greatly accelerated by the addition of certain reagents, with the .. of producing a precipitate which, in fall. ing, will carry down with it the minute particles of solid matter that are suspended throughout the mass. Lime is the substance most usually employed. It is introduced in the form of milk of lime, and in the proportion of about one ton of lime to one million gallons of sewage. en thoroughly mixed, the liquid is left at rest, and a rapid separation of the sewage follows, into a comparatively clear supernatant, liquid and , a glutinous precipitate or “sludge.” . The sludge has little value as manure, for the best agricultural constituents of sewage are contained in solution, and very little of the soluble matter is carried down in the deposit. The sludge is dried by being strained over beds of slag, p into blocks for *:::::: and got rid of by being burnt or dug into the ground or thrown into the sea. It has been used in the manufacture of bricks and of cement (Scott's process), but in general it can be disposed of only at a loss. The clarified effluent still contains dissolved organic matter, and may be admitted into running streams only when a high standard of purity is not compulsory. When, however, the volume of the running water which it enters is relatively very large a quick purification takes place by means of the oxygen which the water carries in solution. The lime process is practised, without further purification of the effluent water, at Leeds and at Burnley. At Bradford, after Foo by lime, the effluent is filtered through beds of cokereeze. At Birmingham the sewage of 600,000 people, after clarification by lime (which also serves to neutralize the acid contributed by manufactories), is used to irrigate a farm of 1200 acres. : Very many patents have been obtained for the precipitation of sewage by other chemicals in place of or in addition to lime. In Hillé's process lime is the chief ingredient, with tar and chloride of magnesium or calcium added. . At Coventry the precipitants are sulphate of alumina, protosulphate of iron, and lime, and the effluent is afterwards filtered through land. in the proportion of 1 acre to 5000 of the population. !.." Sillar's “ABC” process, wērked by the Native o: to slu which has considerable value as manure. An emulsion of clay and carbon with a little blood is first mixed with the sewage; a
precipitating solution of alum is then added, and the mixtus
is allowed to settle. The process gives a remarkably clear effluent; brickwork. The bricks are laid over a templet made td
practically the whole of the insoluble constituents of the sewage and a portion of the dissolved impurities are carried down in the precipitate, which, when , dried and ground along with some sulphate of magnesia, is sold under the name of native guano. The ABC process has been in successful use for nine years at Aylesbury, where the “guano.” finds a sale at 70s. per ton. In 1870 the Rivers Pollution Commissioners reported unfavourably on the process, a fact which may have prevented its adoption by other towns, but it has since then received the approval of many specialists. A recent protracted investigation by Dr C. M. Tidy and Prof.
Dewar showed that the percentage of oxidizable organic matter of sewers, either in
removed by the process ranges from 75 to 86—a result, in their judginent, satisfactory. At Leeds, where the process was tried for a time, it was given up because the effluent was purer than the river into which it ran. and the simple lime-process, which costs less but gives a less clear effluent, was adopted in its place. Much difference of opinion still exists as to the relative merits of broad irrigation, ill.i.a through land, and chemical treat
* - mont, as means of disposing of sewage. That either of the two 7 parts of sand and first plans or a combination of them both can be made to yield a
satisfactory solution of the sewage problem, from a hygienic point of view, seems unquestionable. That chemical treatment, especially if supplemented by filtration through land, will also purify well, is generally admitted. No process of effective purification is now expected to yield a profit; but the question of cost, on which the choice of a system principally turns, is too extensive to be touched in this article.
II. THE CONVEYANCE OF SEWAGE.-For small sewers, circular pipes of glazed earthénware or fire-clay or of moulded cement are used, from 6 inches to 18 inches and even 20 inches in diameter. The pipes are made in short lengths, and are usually jointed by passing the end or spigot of one into the socket or faucet of the next. Into the space between the spigot and faucet a ring of gasket or tarred hemp should be forced, and the rest of the space filled up with cement, not clay. The gasket prevents the cement from entering the pipe, and so obstructing the flow; at the same time it forms an elastic packing which serves to keep the successive lengths of pipe concentric, even if the cement should fail. The pipes are laid with the spigot ends pointing in the direction of the flow, with a uniform gradient, and, where practicable, in straight lines. In special positions, such as under the bed of a stream, cast-iron pipes are used for the conveyance of sewage. Where the capacity of an 18-inch circular pipe would be insufficient, built sewers are used in place of earthenware pipes. These are sometimes circular or oval, but more commonly of an eggshaped section, the invert or lower side of the sewer being a curve of shorter radius than the arch or upper side. The advantagé of this form lies in the fact that great variations in the volune of flow must be expected, and the egg-section presents for the small or dry-weather flow a narrower channel than would be presented by a circular sewer of the same total capacity. Figs. 1 and 2 show
Fics. 3, 2–Forms of Sewers. two common forms of egg-sections, with dimensions expressed in terms of the diameter of the arch. Fig. 2 is the more modern form, and has the advantage of a
sharper invert. The ratio of width to height is 2 to 3. Built sewers are most commonly made of bricks, moulded to suit the curved structure of which they are to form part. Separate invert blocks of glazed earthenware, terra-cotta. or fire-clay are often used in combination with
the section of the sewer, and are grouted with cement, | An egg-shaped sewer, made with two thicknesses of brick, an invert block, and a concrete setting, | is illustrated in fig.
3. Concrete is now very largely used in the construction
combination with brickwork or alone. For this purpose the concrete consists of from 5 to
gravel or broken stone to 1 of Port
SNNSSS ring, or as the sole FIG. 3.-Blick Sewer. material of construction by running it into position round a mould which is removed when the concrete is sufficiently set, the inner surface of the sewer being in this case coated with a thin layer of cenent.
In determining the dimensions of sewers, the amount of sewage proper may be taken as equal to the water supply (generally about 30 gallons per head per diem), and to this must be added an allowance for the surface water due to rainfall. The latter, which is generally by far the larger constituent, is to be estimated from the maximum rate of rainfall for the district and from the area and character of the surface. In the sewerage of Berlin, for cxample, (one of th’ most recent instances of the combined water-carriage system applied on a large scale), the maximum rainfall allowed for is 4 of an inch per hour, of which one-third is supposed to enter the sewers, lm any estimate of the size of sewers based on rainfall account must of course be taken of the relief provided by storm-overflows, and also of the capacity of the sewers to become simply charged with water during the short time to which very heavy showers are invariably limited. Rainfall at the rate of 5 or 6 inches per hour has been known to occur for a few minutes, but it is altogether unnecessary to provide (even above storm-overflows) sewers capable of discharging any such amount as this; the time taken by sewers of more moderate size to fill would of itself prevent the ão. from them from reaching a condition of steady flow ; and, apart from this, the risk of damage by such an exceptional fall would t warrant so great an initial expenditure. Engineers differ widely in their estimates of the allowance to be made for the discharge of surface water, and, no rule can be laid down which would be of general application.
In order that sewers should be self-cleansing, the mean velocity of flow should be not less than 2% feet per second. . The gradient necessary to secure this is calculated on principles which lave been stated in the article HYDROMECHANICs (q.v.). The velocity of flow.
where i is the inclination, or ratio of vertical to horizontal distance; m is the “hydraulic mean depth,” or the ratio of area of section of the stream to the wetted perimeter; and c is a coefficient depending on the dimensions of the roughness of the channel and the depth of the stream. A table of values of c will be found in § 90 of the article referred to. This velocity multiplied by the area of the stream gives the rate of discharge. Tables to facilitate the determination of velocity and discharge in sewers of various dimensions, forms, and gradients will be found in Mr Latham's and other practical treatises. Where the contour of the ground does not admit of a sufficient gradient from the gathering ground to the place of destimation, the sewage must be pumped to a higher level at one or more points in its course. To minimize this necessity, and also for other reasons, it is frequently desirable not to gather sewage from the whole area into a single main, but to collect the sewage of higher portions of the town by a separate high-level or interception sewer. • , a " Sewer gas is a term applied to the air, fouled by mixture with gases which are formed by the decomposition of sewage, and by the organic germs, which it carries, in suspension, that fills the sewer in the variable space above the liquid stream. It is universally recognized that sewer gas is a medium for the conveyance,
Ventila. *ion of sewers.
I}omes. tic sewerage. Primary requisites.
of disease, and in all well-designed systems of sewerage stringent precautions (which will be presently described) are taken to keep it out of houses. It is equally certain, that the dangerous character of sewer gas is reduced, if not entirely removed, by free admixture with the oxygen of fresh air. Sewers should be liberally ventilated, not only for this reason, but to prevent the air within them from evor having its pressure raised (by sudden influx of water) so considerably as to force the “traps” which separate it from the atmosphere of dwellings. The plan of ventilation now most approved is the very simple one of making openings from the sewer to the surface of the street at short distances, generally shafts built of brick and cement, —and covering these with metallic gratings. Under each grating it is usual to hang a box or tray to catch any stones or dirt that may fall through from the street, but the passage of air to and from the sewer is left as free as possible. The openings to the street are frequently made large enough to allow a man to go down to examine or clean the sewers, and are then called “manholes.” Smaller openings, large enough to allow a lamp to be lowered for purposes of inspection, are called “lampholes,” and are often built up of vertical lengths of drain-pipe.
To facilitate inspection and cleaning, sewers are, as far as possible, laid in straight lines of uniform gradient, with a manhole or lamphole at each change of direction or of slope and at each junction of mains with one another or with branches. The sowers may advantageously be stepped here and there at manholes. Sir R. Rawlinson has pointed out that a disserence of level botween the entrance and exit pipes tends to prevent continuous slow of . sewer gas towards the higher parts of the system, and makes the ventilation of each section more independent and thorough. When the gradient is slight, and the dry-weather flow very small, occasional jiushing must be resorted to. Flap valves or sliding penstocks are introduced at manholes; by closing these for a, short time sewage (or clean water introduced for the purpose) is dammed up behind the valve either in higher parts of th. scWict or in a special flushing chamber, and is then allowed to advance with a rush. Many self-acting arrangements for slushing have been devised which act by allowing a continuous stream of comparatively small volume to accumulate in a tank that discharges itself suddenly when ful!. A very valuable contrivance of this kind is Mr Rogers Field's siphon flush tank, shown in fig. 4. When the liquid in
the tank accumulates so that it reaches the top of the annular siphon, and begins to flow over the lip, it carries with it enough air to produce a partial vacuum in the tube. The siphon then bursts into action, and a rapid discharge takes place, which continues till the water level sinks to the foot of the jià. COWer. III. DoNESTIC SEWERAGE.-In the water-carriage system each house has its own network of drain-pipes, soil-pipes, and waste-pipes, which lead from the basins, sinks, closets, and gullies within and about the house to the common sewer. These must be planned to remove sewage from the house and its precincts quickly and without leakage or deposit by the way; the air within them must be kept out of the dwelling, by placing a water-trap at every opening through which sewage is to enter the pipes, and by making all internal pipes gas-tight; the pipes must be freely ventilated by a current of fresh air, in order to oxidize any deposited filth and to dilute any noxious gas they may contain; finally— and this is of prime importance—the air of the common sewer must be rigorously shut out from all drains and pipes within the house. To disconnect the pipes of each individual house from the atmosphere of the common sewer is the first principle of sound domestic sanitation. When this is done the house is safe from contagion from without, so far as contagion can come through sewer gas; and, however faulty in other respects the internal fittings may be, the house can suffer no other risk than that which arises from its own sewage. Protection against the passage of gas through openings which admit of the entry of water is secured by the familiar device known as the water-trap. The simplest and in many respects the best form of trap is a )ent pipe or inverted siphon (fig. 5) which is sealed by water lying In the bend. The amount of the seal (measured by the vertical
distance between the lines a and b) varies in practice from about , an inch to 3 inches. If the pressure of air within the pipe, below
the trap, is greater than that of the air above the trap by an amount exceeding the pressure due to a column of water equal in height to. the seal, the trap will be forced and air will bubble through. This is one way in which a trap may fail, but this may be prevented by sufficient ventilation of the pipe below the trap. Other folio of failure are, however, only too numerous. H f the pipe is disused for some time, the water may eva
porate so considerably as to break the seal. The pipe, •
Fig. 5.-Common Water
of water rush down the *:::::: Trap. c from a closet or sink which discharges into it at some higher point. As the water
passes the junction with the branch d it will produce a partial vacuum in the branch, and so tend to suck over the contents of the trap. This process, which is sonmetimes called the siphonage of traps, can be guarded against by ventilating the branch, either by a separate ventilating pipe leading to the open air or by a pipee (shown by dotted lines) connecting the top of the branch d with a point sufficiently far up on the soil-pipe to be above the column of water which is passing the junction. One more imperfection in traps may be named. The experiments of Dr Fergus have shown that the water in traps will allow gases to pass through by absorbing the
gas on one surface and giving it off at the other. It is improb
able that this action occurs to such an extent as to be dangerous
by permitting the transfer of disease germs from one to the other side. Apart from any risk of this kind, however, it is clear that a
trap is open to so many possibilities of failure as to form a very in
sufficient barrier between the air of a room and the foul air of a sewer.
Nevertheless the practice was until very lately almost universal, and is still far from uncommon, of connecting closets, sinks, an
even bedroom basins with common sewers by a continuous system of piping, in which the only safeguard against the entry of sewer gas is a single trap close to each sink or basin. This means that sewer gas, charged with the infection of a whole community, is brought within a few inches of the atmosphere of the dwelling, ready to contaminate it whenever the trap fails from any of the causes which have been named, or whenever, by a flow of water through it, the seal is sufficiently disturbed to allow bubbles of gas to escape into the room.
The remedy for this lies in having, at any convenient point on
each house-drain, a disconnecting trap which separates the house
Eno open won
system from the sewer, and so establishes what # went alariots
may be called an outer line of defence. Any accidental leakage of sewer gas through it then does no more than cause a comparatively slight pollution of the air within the house-drains, and if these are well ventilated the effects of this are insensible. At each individual basin or other fitting a trap is still required, but its function is now merely to shut out the air of the house-drains from the rooms, and, as the air of the house-drains is no longer polluted by connexion with the sewers, the occasional failure of this function is a matter of comparatively small moment. Further, the disconnecting trap on the house-drain furnishes a convenient place of access for fresh air; and the ventilation is completed by carrying the highest point of each soil-pipe or waste-pipe up to the level of the roof and leaving it open there. This arrangement will be understood by reference to fig. 6, which shows a soil-pipe, open at its upper end, discharging into a house-drain in which there is a disconnecting trap provided with an open grating for the entry of air. The soil-pipe is ventilated by a current of air which (usually if not always) flows o: This not only dilutes any gases that are produced in the pipe, but quickly oxidizes any foul matter that may adhere to the sides. Care must be taken to avoid having the upper end of the pipe open near windows or under eaves. In the figure |}
is scarcely necessary if the T
branch ; short. Another o construction is to carry a "soo" distinct ventilating pipe up from the top of the branch to a point above the roöf; and where several fittings discharge into one soil-pipe, the same ventilating pipe may be made to serve for all. An example of the latterarrangement is shown in fig. 10. The form of disconnecting trap shown in fig. 6 is that of. Mr
FIG. 6.-House-Drain properly disconnected from sewer, and ventilated.
Thouse-drains and soil-pipes. . The same trap is shown to a larger scale in fig. 7, where it appears imbedded in concrete and covered by a built manhole, which gives access to the trap in case of its becoming choked. The manhole may have an open grating at the top; or the top may be closed by a solid plate (if a grating there be for any reason inadmissible), in which dase a yentilating shaft is carried from the manhole to some other opening. Fig. 7 shows such a shaft leading to a grating which is placed Vertically in a neighbouring wall. Among other good forms of disconnecting trap, more or less like Buchan's, mention may be made of Weaver's, Potts's, and Hellyer's,
Fig. 7-Buchan Trap and Manhole, with ventilating grating in wall.
An arrangement of double disconnecting trap is illustrated in fig, 8. Any sewer gas forcing the trap next the sewer is still kept back by the upper trap and will escape by a grating or open ventilating shaft which enters at A, while air to ventilate the house-drain enters the upper trap from the manhole. This arrangement no doubt gives more absolute protection than a single trap of the kind already described, but it is probable that (except in cases where the sewers are very foul and liable to frequent excess of pressure) the advantage is so slight as to be more than counterbalanced by the greater liability to accidental stoppage and greater complexity which this arrangement entails.
The extent to which it is permissible or advisable in practice to allow several fittings to discharge into a single waste-pipe or soil-pipe will vary in different cases. We can recognize a broad distinction between sewage from closets and urinals, liable to the most dangerous taint should disease occur within the house, and the comparatively innocuous sewage that comes from basins, baths, and sinks. Some sanitarians go so far as to advise that these two
classes of sewage should be kept absolutely apart within the house,
by the use of a complete double system of house drain-pipes." This, however, is an extreme measure ; no reasonable objection can be urged against the discharge into a water-closet soil-pipe of water from a bath or washhand basin in the same room, except perhaps that if the soil-pipe is of lead its corrosion is hastened by hot water; and the additional flushing which the soil-pipe so receives is a distinct advantage. But to eonnect a water-closet soil-pipe with sinks and basins in other apartments is to multiply possibilities for the spread of disease within the house, and it is strongly advisable to convey the waste from them by a separate pipe, protected from the sewer by a disconnecting trap of its own with a gratin
open to the air. This applies with special force to the washhan basins that are often fixed in bedrooms and dressing-rooms.' Nothing could be more dangerous than the usage—of which many good houses still furnish instances—of multiplying these conveniences without regard to the risk they involve, and making this risk as great as possible by placing each in direct communication through an ordinary trap §§ the soil-pipe, itself perhaps unven#. and provided with no disconnexion from the sewer. Even when the drain or soil-pipe is ventilated and disconnected from the sewer, no bedroom basin should, under any circumstances, be allowed to discharge into it without first passing a separate open trap. On the other hand, a bedroom basin may be o: perfectly
safe by leading its waste - pipe (trapped e A At 1 N 6 under the basin in the (* usual way) into an à
open-air channel which “o communicates with the sewer by a surface-trap' " or gully outside the house (fig. 9). Similar treatment should be" adopted in the cases of pantry and scullery sinks. Under most plumbing fixtures it is . • * * * usual to place a safe-tray to receive any water accidentally spilt. The discharge pipes from these trays are sometimes, but very ob-, jectionably, ..Pinto the waste-pipe or soil-pipe below the fixture. The proper method of providing for the discharge of water spilt into the safe-tray is to lead a pipe from it through the wall and allow it to end in the open air (fig. 10, where each of the safe-tray drains is marked “waste-pipe”); a flap valve fixed on the end will serve: if need be, to keep out draught. -Overflow-pipes from cisterns used for dietetic purposes should bel led, in the same way, into the open air and not into soil-pipes or waste-pipes (fig. 10). Traps on them cannot be depended on to remain sealed, and any connexion of an overflow-pipe with a soilipe would result in allowing foul air from the pipe to diffuse itself over the surface of water in the cistern—a state of things peculiarly likely to cause pollution of the water. When a cistern is used only for water-closet service, its overflow-pipe may properly be led into the basin of the closet. Rain-pipes, extending as they do to the roof, are sometimes used
to serve as ventilating continuations of soil-pipes and waste-pipes. The practice is open to serious objection, for it discharges the drain air just under }. eaves, at a place where air is generally ; drawn into the house. The ventilating end of a soil-pipe shoul be carried to a higher level, as in fig. 6, clear of the lower edge of the roof. It is better to restrict rain...pes to their legitimate function of taking surface water from the roof, or at most to allow them to receive slop-water from sinks and basins, and to make them terminate in or over open traps from which a connexion is taken to the house-drain or sewer (fig. 9). In figs. 10 and 11 the sanitary fittings of a small house are shown by diagrams, which should be carefully studied as exemplifying a well-arranged system. Two closets, and a bath and basin in the closet apartment, discharge into a soil-pipe on the right; and the branches (except that of the basin) are ventilated by pipes leading to a separate air pipe, which, like the soil-pipe, is carried above the roof. The overflow of a cistern which supplies bath, basin, and boiler is carried out to the open air, and so are the waste-pipes of the leaden safe-trays. A separate cistern supplies each watercloset, and its overflow opens into the closet basin. A rainpipe (in the middle of the figure)
receives a bedroom basin waste, and leads by a 4-inch drain’ to a ventilated grease-box, into which, the scullery sink - and wash- swort: tubs and another rain-pipe also discharge. Finally, the whole system is protected by . a Buchan trap in a built manhole, which if covered with a grating. - House-drains, that is to say, those parts of tho domestic system of drainage which extend from the soil-pipes and waste-pipes to the sewer, are made of glazed fireclay pipes, generally 6 inches but sometimes only 4 inches in diameter. A larger size than 6 inches is o if ever desirable. The pipes are spigot-and-faucet. jointed, and the joints should be made with cement in the manner already described for sewers. When, as is often unavoidable, the house:drain has to pass under a part of the house, or to come from back to front, iron o jointed with lead and coated with an anti-corrosive compound are preferred to fireclay pipes, as giving a better security against the production of loaks by the settling of the soil and other causes. Soil-pipes, when carried ‘lown inside the house, are of either lead or iron; when outside the house they are usually of iron... An outside soil-pipe is obviously preserable to an inside one; if the arrangement of the buildin omakes an inside soil-pipe necessary, care must be taken that it shafi be easily accessible for inspection at all parts of its iength. The usual diameter is 4 inches. For the sake of good ventiation it is desirable to continue the soil-pipe to a point above the roof without reduction of diameter rather than apply a smaller ventilating pipe. Amongst reasons for ventilation one remains to be mentioméd. that, owing to the corrosive action of sewer gas, the life of the soils o is greatly shortened if provision for the free circulation of air 9.Wänting or insufficient. . A closed soil-pipe becomes in time pitted with holes, especially in the upper parts of its length. Defective joints in soil-pipes and waste-pipes, particularly where £hey connect with drains, closet-basins, sinks, &c., are another frequent cause of leakage. Any want or air-tightness in drains * soil-pipes within a dwelling leads to the pollution of the air, not
Fig. 11–Plan of the Drains in fig. 10.
merely by diffusion, but by an actual in-draught, for generally the air of the house has its pressure reduced by chimney draughts to a value slightly lower than that of the air outside. The house, in fact, ventilates itself by drawing in air from the pipe at any hole, a fact which may easily be demonstrated by holding the flame of a taper near the hole. - Various experimental methods are used of detecting such leaks as would admit foul air to the dwelling. Of these the best is the “smoke test.” It consists of filling the house-drain, soil-pipes, and waste-pipes with a dense and pungent smoke, any escape of which into the house is readily observed by eye and nose. A quantity of cotton-waste soaked in oil is lighted, and its fumes are blown into the house-drain by a revolving fan, at the ventilating cover of the disconnecting trap, or at any other convenient opening. Smoke soon fills the pipes, and begins to escape at the roof. The upper ends of the pipes are then closed, and the house is searched for smoke.” Another test, especially applicable to those parts of drains that are laid under houses, is the hydraulic test, which consists in stopping up the lower end of the pipe, filling it with water, so as to produce a moderate pressure, and’ then observing whether the level of the water falls. This test, however, is too severe for anv but new and very well constructed drains. Every basin, sink, or other fittin oy a bend on the wastepipe or some other form of trap. A brass cap, screwed on a ferule which is let into the pipe on the bend, facilitates cleaning (fig. 5). The warm wastewater from pantry and R. scullery, sinks contains N much grease, and should be discharged into a grease box (fig. 12) where the water becomes cool and deposits its grease before overflowing into the drain. To collect surface water from o floors, areas,t court-yards, &c., an open trap or gully is used. Fig. 9 shows a simple and good form of open to - i trap; but if the water is liable - fo to carry down sand or earth o a gully (fig. 13) is more suitable. Even in this simple fittingaremarkable ingenui of error has been displayed. Many of the forms Hood by builders are bad either because of an insecure seal, a narrow outlet, or a tendency to gather filth. One in particular; the well-known “Bell” trap, is an example of nearly everything a trap should not be. Water-closets used to be almost invariably of the “pan” type, but wherever sanitary reform }. been . preached to any purpose the pan closet is giving place to cleane, and wholesomer patterns. The evils of the pan closet will be evi, dent from an inspection of fig. 14. At each use of the closet the hinged pan a is tilted down so that it discharges its contents into the container b. ' The sides of the container are inaccessible for cleaning, and their upper portions are out of reach of the ushing action of the pan. They gradually become coated with a foul deposit. A gust of tainted air escapes at every use of the closet; and it rarely happens that the container is air-tight, and §. the filth it has gathered does not cause a smell even in intervals of disuse. To make matters worse, o o to: !". o: aro provided with the kind of trap shown in the sketch, called the D §. which is FIG. 14. ran watercot. also liable to become a gathering place for filth. , Even with an ordinary trap, however, the pan closet remains so bad that its use is to be strongly condemned. . . . - - - A much better closet is the valve or Bramah closet, an excellent
1 A novel plan of making the smoke test has lately been introduced, in which Smoke is iš. so a "smoke rocket" or cake of slowly combustible compoun which is lighted and placed in the drain.
FIo. 12.-Grease Trap.