SEW

423

SEW

hn<T. Wate r

in the junctions ; the extent to which the't wi |j‘ J ' e °an be carried, is to be determined by practice;" 1 depend . - - -

to some extent on the fall of the main line.6 >U ere / e sewers are constructed with the intention of beingl lr °Perl ^° r * ns P ect ' on > is necessary that they should beV tli e ^ Ven tilated ; otherwise, the noxious gases generatedhal; 0 j. 8 ® Wa ge, would forbid entrance, except at considerablef lr eo n „.. * e ! fatal accidents have occurred, for want of such

5 'C Um - ^'lie usual plan for effecting this, is to construct" arr °w, and tapering shaft from the crown of the^tQun, 0 tb e roadway ; but this practice is objectionable, on^ pf the gases vitiating the atmosphere, and thusand it does appear somewhat inconsis-

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c °Ur a

Ht, th^ ,n ® disease . ^ __

( ,^ at while gullies are trapped to prevent the ascent ofav,il > other shafts are constructed for the purpose

■' eilt ilar' n ° >t. It is true, there is some advantage gained in>8inu g > tlle vertical shaft, but not sufficient, it may be’''ctliQ.) d> to counterbalance the inconsistency. Severali^oa,, ® ba ve been attempted, to obviate this difficulty :

may ke mentioned, the connection of the venti-

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wi ‘h the ,

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a furnace: the ventilation by steam-jet, &c. : eachV . ,C h Dlnn. 1_V- -_i_-_!<• , .

H - V le rain-water pipes of the houses, and extending5lt diroi° n ?' dera ' de be >gkt above the houses; the passage of the

f ' Pit) ^ un ® **ave been more or less successful. If we adopt0t thg ~? e ' v ers, all difficulty on this score is at once obviated,?'■(! lj b'pea themselves are impermeable, and if the gullies'Vu ^ 8 ®'^rains be properly trapped with syphons or flaps,i t ^ b e little dan ger of the escape of noxious vapours;% Se l v Ust be remembered, that in this case, the sewers'«y ,j 0 es ar e not required to be ventilated, seeing thatj/aitii^, a°t admit of passage by a man. That they are® f itj g however, to a certain extent, is very probable;ji^tfer known, that the rapid motion of a stream of

s as th P roduce a sensible current of air, and in propor-^' v er Si s e Ve iocity of flow is greater in small than in large,N e ‘ ...Will their ventilation be more completely effected:a eed '!■’ as the deposit is likely to be less, there will behi j ar °‘ Ventilation.

;i *n 3 0 j. sewers, it is necessary that there should be readytN " C(;a access to them, and this is best provided for by side-' Which consist of vertical shafts descended by ironand covered with cast-iron

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flaps.

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Of s i^„ 8te P-irons,

>t> s e tS aie f'aeed at any convenient spot, at the sided|e tat) ,? r ’ generally in the footpath, where the sewer isH-cl , alr " ' ‘ ‘ ‘ ‘ ‘ ‘ _

(J>d

e of the road, and from the bottom of the shaftPassage is carried with a slight inclination tinder

sewer, the lowest level of the bottom

> C y , bto the OC-VYdj LI1C 1VYYCOI A'iY'

® fo 18 inches above the invert.

^ r y off t j 1<i( l u ire to be constructed at certain intervals, toOf by 16 Sui 'face-water from the roads. The water isaaf lat ‘ ng3 * n fbe channel of the road into a cesspool

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° *he whence by an overflow-pipe with syphon trap

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The grating should be made to open, orthe cesspool, in order to remove the

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lv itu> . rec luisUe.f (; a<j\v ® tre ated upon the subject of drainage generally,li^'fes ij 0 ,? to tbe consideration of house-drainage, which* d tai * e ' v reir >arks. The old system of carrying the'hu °' v a . S e jato the main-lines, consisted simply in lay-lh.. thp ■ Ur am from each house, connected at. the one enr)> ! 8,a ks,

from each house, connected at the one endt^' 1 * Se We '“°- 8 > water-closets, &c.; and at the other with thesSi“ i ' h ran in the centre of the road.

Amongst

O th e ' l m P r °vements, a new plan has been adopted, byIs t ba ck of araina ge of the house is conducted into a pipe atftif^ed i l be premises, and by it into a main sewer ; thisC t ^ r linage; and the old system, front-drainage ;111 tbe former case, the sewage is collected at the

back, in the latter it is collected at the front of the houses.The system of back-drainage is certainly in many respectsan improvement upon the old, but it is not so universallyapplicable as some persons would lead us to believe ; it pro-vides a convenient variation, but not an extensive substitute.One great improvement is effected by carrying the drainageat once away from the premises, instead of its running underthem, as before. The objections to the old system in thisrespect, are, the passage of the drains under the houses,whereby, if not perfectly constructed, the effluvia is likely tobe spread all over the interior ; and the inconvenience whichis thereby occasioned in case of stoppage, or other necessaryexamination or repair which involves the removal offloors, &c., and the opening of drains in the house ; mattersnot only inconvenient, but sometimes dangerous, on accountof the escape of effluvia. In some cases, where the old brickdrains have been employed, and, as is not unfrequently thecase, improperly constructed, the drainage has been allowedto escape through crevices in the brick-work, and saturatethe foundations of the premises ; this is frequently the causeof damp basements, and of unpleasant and noxious odours inthe lower part of the house. A further objection exists inthe frequent apertures required to be made into the mainsewer for the insertion of the house-drains, and the manyinterruptions which are occasioned in the flow of the sewagein the main sewer, by the discharge of so great a number ofhouse-drains.

These objections are obviated almost entirely by the newsystem ; the drains, instead of being carried through thehouse, are at once removed from it, and the dangers and in-convenience attending the old practice entirely done awaywith. Such at least is the case in by far the majority ofinstances: occasionally, where the position of water-closets infront of the house requires the drains to be brought throughthe house to the back, the employment of the new systemwould not be so advantageous ; the carrying of drains fromsinks through the house, is not so objectionable. The largesewers will not be interfered with, except at distant intervals,for the insertion of the main back-drain, discharging thesewage of a block of several houses. There are several otheradvantages attending the new system, amongst which may bementioned the following :—The flow of sewage is very con-siderably improved by its concentration into one drain,instead of being spread over many; the frictional surface isalso much reduced. In the old system, the occasional flowof water from each house was so inconsiderable as to producea mere dribble, which flowed sluggishly, and deposited itssolid matters in abundance, under the very dwellings; itwas but a small portion that eventually reached, and wasdischarged into the sewer ; whereas, where the back-drain-age is adopted, the water is discharged almost immediatelyinto the main back-drain, and the collection of the sewage ofall the houses therein produces a considerable volume, suffi-cient at all times to keep up a moderate flow into the mainsewer, and thus prevent deposit ; if, however, deposit shouldoccur, it is less objectionable than where it takes place underthe house. There is a fair objection to this system whenstoppage does occur, for the stoppage in one place will occa-sion the same in every house which happens to be situatebetween the stoppage and the first inlet ; under the oldsystem, this would not take place. In the separate system,each occupier is subject to the inconvenience occasioned onlyby his own negligence or carelessness, whereas in the com-bined system he is, to a certain extent, at the mercy of hisneighbours ; when, however, we take into consideration theimproved flow in the main back-drain, and the less probabilityof stoppage, this objection will not have so great weight.

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