function that makes a channel for carrying sewage a sewer or a drain, but whether it drains more than one house, if it does, and the houses so drained belong to, or are tenanted by different persons, although the drain may be only a 6-inch pipe, it is a sewer under the Act, save under the Metropolis Local Management Act, it may be the combined drainage of a block of buildings sanctioned or ordered by the authority. As may easily be conjectured from this somewhat loose definition, there are many cases in which it is doubtful whether the channel for the conveyance of sewage is a "drain" or a "sewer."

It is in some cases advantageous for a main sewer not to be absolutely water tight, but drains for houses should in all cases have sound joints; a proper drain for the carrying off of sewage is a water tight tube; on the other hand an agricultural drain, or what is called a "weeping" drain, which is sometimes put in the basements of damp houses, is a channel for the reception of the water in the soil, the subsoil water, and the joints are open and uncemented.

(126) Brick Drains and their Defects.

House drains are now invariably made of glazed socket pipes, or in some cases of iron pipes; the evil of square brick, or of barrel drains, the common construction of forty years ago, is well set out in the following passage from the report of the Metropolitan Sanitary Commission, 1848:

"It is a first principle that where matter is conveyed by several small currents, if these small currents are united into another channel, of a proper form and inclination, the quicker will be the flow of the united currents, and the more powerful the sweep of any matter in suspension. From the practical observations of sewers kept free from deposit, it is manifest that very small currents suffice for the purpose, if the inclination be good, and the flow be concentrated and kept regular, for which additions of small quantities of water, at particular intervals and seasons, it is considered would be sufficient.

"The reverse of these principles generally obtains in practice in the majority of the districts of sewers. In the first place the house drains are so constructed as to spread and impede the streams, and are often kept running separately for unnecessary distances from

the sinks and house gutters. The house drains, too, receiving the water from the small 1-inch leaden pipes of kitchen sinks, are sometimes of sixty times the capacity of these pipes in the smaller houses, they are generally made of bricks in the following form (Fig. 30):—

"The architects and builders generally put in barrel drains to the larger houses in the following form (Fig. 31), made of brick, with porous mortar in the upper portions :

FIG. 31.

"These and the flat brick house drains are generally put in "dry" at the bottom, or without mortar, to let in the water of the land drainage, but they commonly let out at their bottoms or sides, instead of the ends, much sewer water, which permeates the foundation and site of the house, leaving the solid refuse deposited on the surface of the drain to decompose and ultimately choke it up. It is rare to find any house drain of this description without deposit. They are indeed made upon the hypothesis that they will accumulate deposit, and the construction of brick is preferred that the drains may be the more readily opened, and the

deposit from time to time removed. One of the surveyors of the Surrey and Kent sewers, Mr. Joseph Gwilt, the author of an encyclopædia of architecture, prescribes a size of drain of 5 feet square for a moderate sized mansion to enable a man to get at it to cleanse it from time to time. The Metropolitan Building Act prescribes that the least size of house drains shall be nine inches; the hypothesis being that, inasmuch as even these drains accumulate deposit, drains still larger are desirable.

"Now it is proved that whilst house drains of such size and construction as have been enforced by the Commissioners of Sewers accumulate deposit, drains of a smaller size keep perfectly clear. Thus, whilst a 12-inch drain, which is required by the Kent and Surrey, and the Tower Hamlets and the City Commissioners, accumulates deposit and generates noxious gases, a tubular drain, of nine times less capacity, or of 4 inches in diameter, or proportional to the house of from 3 to 6 inches keeps perfectly clear. Even 3-inch drains convey away the refuse from middle sized houses and keep perfectly clear, whilst the larger permeable brick drains are choked up."

Mr. Roe, the (then) surveyor of the Holborn and Finsbury division of sewers, who led the way in systematic improvements in the form of construction of main lines of sewers in the metropolis, made for the Commission experiments on the rate of flow of water through the common brick drains for houses, as compared with the rate of discharge through earthenware drains of the same capacity, and with the same run of water. The general results given are that through earthenware tubes the rates of discharge are increased to an important extent, in the smaller and more frequent forms to the extent of more than one-third. In other words, an economy of one-third the quantity of water to obtain the same result is effected by them, and the general efficiency of the drainage in ordinary runs proportionately augmented. Examples are given on the following page (Table XXVI.).

Besides the general disadvantages pointed out in the above extract from the Metropolitan Commission's report, there are certain other special evils attendant on the use of brick drains in towns supplied with a sewer system; these are the comparative ease with which rats are able to work through the brick-work and make runs, and the general tendency of brick drains to enhance

the cost of maintenance of the sewers. A brick drain in connection with a brick sewer, if at all defective at the junction between sewer and drain, soon damages the sewer, by allowing the house sewage to trickle between the sewer wall and the earth, and thus loosen the brick-work.

To summarize the above points, the chief defects of house drains when constructed of brick, are :—

(1) A tendency to deposit.

(2) The velocity of sewage in brick drains is less than in pipe drains, hence they have to be laid at a greater fall.

(3) Brick drains are almost impossible to be made tight, and except they be laid in concrete nearly always leak.

(4) Brick drains are not so easily trapped as pipe drains.

(5) They have a tendency to damage any sewer with which they are connected, and hence to make the cost of the sewer maintenance greater.

COMPARATIVE TIME OF RUN OF WATER THROUGH BRICK DRAINS AND

TABLE XXVI.

The pipes at present in use for drains or sewers, are from 4 inches up to 18 inches, and are made of pipe clay or a mixture of fire and pipe clay; they are salt or glass glazed. They are provided with collars or sockets at the one end, which receives the spigot end of the next pipe, the joints being filled in with Portland cement; clay is often used instead of cement but the practice is to be discountenanced, for the clay is liable to wash out. There are certain patent joints, such as Stanford's, that do not require cementing, a sort of ball joint is made, and a little grease renders all tight: this

deposit from time to time removed. One of the surveyors of the Surrey and Kent sewers, Mr. Joseph Gwilt, the author of an encyclopædia of architecture, prescribes a size of drain of 5 feet square far o moderate sized mansion to enable a man to get at it inspected. Otherwise if anything should be the matter, such as a stoppage, a pipe has to be broken. There are a multitude of ingenious devices for this purpose.

Jennings, for example, supplies a pipe in which the ordinary socket is replaced by a divided ring, the one half can at any time be removed and the pipe lifted out. Messrs Doulton make a "lidded" pipe, in which a third of the pipe can be taken off the whole length. There are also "capped" pipes to be had; in these elliptical holes are cut in the upper portion, and the openings are closed by well cemented covers. It is however not so easy to push long lengths of clearing rods through an elliptical hole of this kind, so that in the author's opinion, access pipes of the Jennings' or the "lidded" type, will be found more generally useful.

The following axioms with regard to house drains are accepted:

All joints must be watertight.

The larger pipes receive the smaller ones, and not vice versa, thus 12 inch may go into 15 inch, 9 inch into 12 inch, 6 inch into 9 inch, 4 inch into 6 inch, and 2 inch into 4 inch pipes.

Never lay drain pipes underneath a house if it can be avoided. Where one drain joins another, the line of junction should be that of a curve, or an obtuse angle. T and L shaped junctions

are wrong.

When a drain changes its direction, there should be some means of inspection.

(128) Fall of House Drains.

The "fall" of a drain is the angle it makes with a horizontal plane, and is ascertained on the same principles as that of any sloping surface. The least fall should be one in forty-eight, that is inch to a foot; a greater fall is preferable, but as in the case of sewers, a drain may have too great a fall; for instance, a perpendicular soil-pipe entering a sewer, as in the diagram Fig. 29 is apt to produce a deposit.