The sense in which we shall use the term “drain” is that defined by the Public Health Act of 1875:—“‘Drain’ means any drain of, and used for the drainage of one building only, or premises within the same curtilage, and made merely for the purpose of communicating therefrom with a cesspool or other like receptacle for drainage, or with a sewer into which the drainage of two or more buildings or premises occupied by different persons is conveyed.”
There can be no doubt that the almost universal system pursued with regard to house drainage is radically irrational and dangerous. As the drains lead into the main sewer or cesspool it is most important that the house-pipes which communicate with the drains should be so connected with them and arranged, as to remove all risk of the foul air of the sewers passing into them through the drains, and thus (should the pipes be imperfect) escaping into and defiling the atmosphere of the house—a very possible contingency for two reasons, first, because the traps connecting the pipes with the drains may be defective, and, second, because the aspiratory power of the warm house is constantly tending to draw air (the sewer air) through the water in the water trap. Instead of making the connection, as is now so universally done, between the sink and closet and other pipes and the drain, by means of a water trap, underneath the basement, this junction should be effected outside the house. The drains should, therefore, always terminate outside, and not under the house; and wherever practicable all house-pipes should be carried outside, and not inside, or between the walls of any dwelling, the objections to which have been already stated. In cases, however, in which this arrangement is impossible of execution, and a pipe can only be carried through the house from the front to the rear, it is far better to take it above the basement than underneath.
The interposition of the water in the trap at the point of union between the house-pipe and the drain is not alone sufficient to effect the necessary amount of disconnection between them. There must be thorough ventilation and communication with the outer air at the point of junction, otherwise there is danger that the emanations from the sewer may find their way into the house, as in the former case.
A great number of methods have been devised for disconnecting the house-pipes and the outside drains, the simplest of which consists in placing the trap just outside the house, in opening the drain on the side of the trap the furthest from the house, and in carrying up from it a four-inch pipe to as great a height as is convenient. By this means any noxious gas that might escape from the drain is diverted from the house, and ascends into and diffuses into the superincumbent atmosphere.
In the arrangement of the house-pipes it is desirable not to carry the pipes which convey away the sink water and the waste water into the closet-soil pipes, but, wherever it can be managed, to let them discharge over a grating into the drain trap. Where we have to deal with soil or water-closet pipes, or with a pipe formed by the junction of these with the waste-water pipe (if such an arrangement is unavoidable), it is most important that there should be complete disconnection between the pipe and the drain by means of one of the many ventilating contrivances so well known to sanitary engineers.
The best material for the manufacture of drain pipes is hard, well-burnt, smooth, and glazed earthenware; bricks and porous earthenware are particularly ill adapted for the purpose; so also are iron pipes, unless they are thoroughly cemented inside.
In the laying of drain pipes care should be taken to place them on concrete, in loose soils, and on well-worked puddled clay, in the case of clay soils. When they are laid in very loose soils it is sometimes necessary, besides employing concrete, to additionally use even piling for the depth of a foot. Leakage and consequent soakage of the soil are sure to take place sooner or later if the drain pipes are not laid on a good foundation, as they are when the drains are badly and carelessly joined.
Messrs Brooke, of Huddersfield, have invented a combined drain and subsoil pipe, the latter, on which the drain pipe rests, being perforated, carries off the subsoil water. This contrivance is adapted for wet soils.
When junction pipes are required for uniting the drain pipes those known as “oblique junctions” only should be used. The junctions known as “square junctions” should be avoided, as they are always sure to become blocked up.