The Public Health Act 1875 contains a considerable number of clauses dealing with the subject of the sewers of a town, but two of the shortest sections in the whole Act, and yet those that involve a considerable amount of work in the town surveyor’s department, are the following:

“Every local authority shall keep in repair[174] all sewers belonging to them, and shall cause to be made such sewers as may be necessary for effectually draining their district for the purposes of this Act”[175] (38 & 39 Vic. c. 55, s. 15).

“Every local authority shall cause the sewers belonging to them to be constructed, covered, ventilated,[176] and kept so as not to be a nuisance or injurious to health, and to be properly cleansed and emptied”[177] (38 & 39 Vic. c. 55, s. 19).

As to what sewers do “belong” to the local authority, the following section of the Public Health Act 1875 states:

“All existing and future sewers within the district of a local authority, together with all buildings, works, materials, and things belonging thereto,

“Except

“(1.) Sewers made by any person for his own profit, or by any company for the profit of the shareholders; and

“(2.) Sewers made and used for the purpose of draining, preserving, or improving land under any local or private Act of Parliament, or for the purpose of irrigating land; and

“(3.) Sewers under the authority of any commissioners of sewers appointed by the Crown,

shall vest in and be under the control of such local authority.

“Provided that sewers within the district of a local authority which have been, or which may hereafter be constructed by or transferred to some other local authority, or by or to a sewage board or other authority empowered under any Act of Parliament to construct sewers, shall (subject to any agreement to the contrary) vest in and be under the control of the authority who constructed the same, or to whom the same have been transferred” (38 & 39 Vic. c. 55, s. 13).

And as to the definition of the word “sewer,” the same Act states:

“‘Sewer’ includes sewers and drains of every description, except drains to which the word ‘drain’[178] interpreted as aforesaid applies, and except drains vested in or under the control of any authority having the management of roads and not being a local authority under this Act.”

The result of this acquisition by the local authority of the sewers in their district is, that in most of the old cities and towns a legacy of very defective and imperfect sewers has been inherited, and considerable expense in their repair and maintenance has thus been entailed.

A great number of books have been written on the subject of sewerage, and much valuable information has been published from time to time, so that it almost seems superfluous to say much upon the subject; however, a few remarks which are particularly applicable to the work of a town surveyor may be of some service.

The word sewerage may be taken as meaning a system of sewers carrying sewage which is the fluid and feculent refuse from dwellings and their yards, &c. Sewage is generally found mixed with rain water from the surface of the streets and roofs of houses, together with the liquid waste products from manufactories,[179] and sometimes, although very improperly, with subsoil water.

A good system of sewerage should embrace the whole of the following requirements:—

(1.) Each sewer should be laid at such a depth as will readily drain the basements of the adjoining buildings.

(2.) Its area and gradient must be so regulated as to make it self-cleansing, and at the same time carry off effectively the maximum quantity of liquid for which it is intended.[180]

(3.) Each sewer should (unless quite impracticable) be laid in straight lines and with even gradients between man- or lamp-holes, and these gradients must not be excessive, or damage may be caused to the sewer. A velocity of about 6 feet per second is sufficient.

(4.) Sewers must be laid at proper levels in respect of their intersection with each other, bearing in mind that they are all generally converging to one point.

(5.) Manholes should be of simple construction; circular brickwork upon concrete is a convenient description. They may be made to serve the additional purposes of ventilating shafts, flushing chambers, junction shafts, storm overflows, and side entrances.

(6.) Tributary sewers or drains should not join the main sewers at right angles unless the bottom of the manhole is so constructed as to give the required curve in the direction of the flow of the sewage, and they should join at a height (if of unequal section) equal to the difference of their sectional diameters, the aim of all junctions being to cause as little disturbance as possible in the proper flow of the liquids along their respective channels.

(7.) Sewers should not be constructed of too large a sectional area, but none should be less than 6 inches internal diameter, as house-drains in this country are never less than 4 inches diameter, and the main sewer should of course be larger than its tributaries. It is also rather difficult to ventilate a smaller sewer than 6 inches, and very little is saved by putting in a smaller sewer than that.

Stoneware pipes of greater diameter than 18 inches should never be used. Where larger sewers are constructed they should be either concrete pipes,[181] or brickwork or concrete should be employed.

The position of the sewer should, if possible, be behind the houses for the following reasons:—

(1.) The waterclosets, sinks, &c., being nearly always at the back, a drain under the house (which is always objectionable) is avoided.

(2.) Economy is secured to the owner of the property, as a shorter length of drain is required than if the sewer was in the front.

(3.) A better fall is usually obtained.

(4.) Where there is a separate or partially separate system of sewerage, a double sewer in the street is avoided.

The only objection to this method being that of the chance of the sewer becoming choked or broken when entry has to be made into private property to repair it, but this ought never to happen after once the sewer has been properly constructed. Of course, where houses are closely packed together it would not be possible to carry the sewer at the back, but where it can be done I agree thoroughly with Mr. Rawlinson, C.B., C.E., &c., who, speaking of this method, says, “I know nothing but good of it.”

Where the sewer is proposed to be taken through any private lands it is necessary to act in accordance with the following clause of the Public Health Act 1875, and serve the necessary notices, a specimen form of which also follows:

“Any local authority may carry any sewer through, across, or under any turnpike road, or any street or place laid out as or intended for a street, or under any cellar or vault which may be under the pavement or carriageway of any street, and, after giving reasonable notice in writing to the owner or occupier (if on the report of the surveyor it appears necessary), into, through, or under any lands[182] whatsoever within their district. They may also (subject to the provisions of this Act relating to sewage works without the district of the local authority) exercise all or any of the powers given by this section without their district for the purposes of outfall or distribution of sewage” (38 & 39 Vic. c. 55, s. 16).

The form of notice necessary to be served before entry upon any lands for the purpose of carrying out any sewerage works may be on the following pattern:—

The Schedule Referred to.

In carrying out works of sewerage the greatest care is necessary in the materials selected and the manner in which the work is executed. Tunnels and shafts must be most carefully timbered, levels very accurately given and adhered to, and for this purpose sight rails and long boning rods can be used with great advantage. In running sands, or where the line of an old sewer is being followed, or in fact anywhere where a good and quick joint is required, “Stanford’s” patent jointed pipes should be used.

“This joint is made by casting, upon the spigot and in the socket of each pipe, rings of durable material, which, when put together, fit mechanically into each other, as in a bored and turned joint; it needs no skilled labour in fixing, only a little grease, allows of slight settlement of the pipes without injury, and requires neither cement, clay, nor other extraneous material, the pipes containing a perfect joint within themselves.”

Breakages sometimes occur in stoneware pipe sewers after they are laid, which generally are found on examination to arise from one of the following causes:

(1.) Laying the pipes on a rigid foundation without recessing the sockets so as to give an even bearing.

(2.) Laying the pipes on foundations which afterwards yield or settle.

(3.) Laying the pipes at too great a depth without protection by concrete or otherwise to resist the pressure of the superincumbent earth, or by not sufficiently punning the filling-in, when a sudden settlement will often crack or crush a pipe.

(4.) Accidental or wilful injuries to pipes which are not noticed before the trench is filled in.

(5.) Laying the pipes at too shallow a depth without protection, when heavy traffic or a falling weight upon the surface will crush or crack a pipe.

(6.) Defective or weak pipes.[184]

The following plates give the different forms of sewerage pipes that are now manufactured in this country, in addition to those of common shapes:

The chokage in pipe sewers generally arises from one or more of the following causes:—

(1.) Improper gradients.

(2.) Insufficient flush.[185]

(3.) Foreign articles finding their way into and choking the sewer.

(4.) Defective joints through which the liquid runs leaving solid matters behind.

(5.) An excess of road detritus or of ashes, through the house closets of the poor, finding their way into the sewer.

(6.) Improper bends in the line of sewer.

(7.) Right-angle or improper junctions being formed with the sewer.

(8.) A collapse of the sewer.

A temporary chokage in a small-sized sewer which does not arise from any structural defect can be speedily and effectually remedied by the use of Ben Reed’s patent drain-cleaning rods, which are probably too well known to every town surveyor to need any description, but in conjuction with man- or lamp-holes and straight lines of sewers they are very valuable.

Before closing this chapter, a few words upon what is called the “separate system of sewerage” may be of use.

The mistake hitherto made has been to try to absolutely separate all rainfall from the sewers, and there is no doubt that a partial separation of the rain-water from the sewage proper has many advantages; but it must be understood that a great deal of the rain-water that falls upon roofs of buildings and in back yards and small back streets must of necessity be carried into the sewers, as well as liquid refuse from manufactories. A partial separation thus carried out has the following advantages:

(1.) It is not necessary to have sewers of enormous diameter.

(2.) The depth of the surface water conduits need not be so great as that which is necessary for sewers.

(3.) The avoidance of road detritus being washed into the sewers.

(4.) Where the sewage has to be pumped or treated chemically or put on the land, the combined system causes an immense unwieldy bulk of liquid to be at times dealt with.[186]

(5.) The sewers may be placed at the back of the houses, a great advantage which cannot be carried out under the combined system.

(6.) The regularity in the amount of flow of sewage.

(7.) The accuracy with which the quantity of sewage may be calculated and the sizes of sewers apportioned.

(8.) Economy both to the general rates and also to individuals in carrying out their connections.

(9.) Where old and defective sewers exist they are often fitted to carry surface water, but are quite inappropriate as sewers.

No rules, however, can be laid down with regard to this question, as each town or district must be treated as the case requires.

In conclusion, I will mention the different methods at present in vogue for the sewerage of towns.

(1.) The combined system, where all sewage, surface water, manufacturers’ refuse, and subsoil waters are carried in the same sewer.

(2.) Similar to the above, the subsoil water, however, being carefully excluded.

(3.) The partially separate system.

(4.) The absolutely separate system, where there are three sets of sewers, one for sewage proper, one for surface water, and one for subsoil water.

(5.) The “Lieurner” system, which professes to remove all sewage by exhausting the air in the sewers and drains.

(6.) “Shone’s” pneumatic ejector system, which is described as follows:—

“The ejectors are cast-iron receivers of a suitable form, placed underground at depths to suit the locality, into which ejectors the sewage flows through the ordinary pipe drains from the houses. As the liquid rises in the interior of the ejector, and when full, it lifts a valve and admits compressed air from an engine which supplies the entire district. The ejectors are thus emptied of their contents, which are blown out in about eighty seconds of time, and the sewage passes through cast-iron main pipes of suitable diameters to the land, or other outlet provided to receive it, or it may be distributed upon the waste land as it passes through.”

(7.) The dry systems, which consist of—

(a.) Earth closets;

(b.) Tubs, as the Goux, &c.;

(c.) Pails, as the Rochdale;

(d.) Middens.

But all these dry systems require some system of sewers to carry off rain-water, slop-water, &c., and in my opinion are not suitable for very large communities.