The drainage of a stable may be defined as the removal by gravitation of fluid which is on or near the surface of the stable.

Drainage may be carried out in two ways, namely, more or less horizontally, which is the only efficient method for the removal of fluid containing animal and vegetable matter, and more or less vertically, as we see when rain falls on sandy ground. In both cases, the removal should be distant as well as complete. The depth of the surface water, which as a rule is shown with a fair amount of accuracy by the distance the surface of adjacent wells is from the surface of the ground, is a reliable measure of the efficiency of the vertical drainage, which, as I have just indicated, is applicable to the removal of only comparatively pure water. In order to keep the ground of the interior and immediate vicinity of a stable in a dry condition, its surface should as far as possible be waterproof, and its drainage should be of the horizontal kind, for which a difference of level is required. Hence, it is advisable to have the floor of the stable raised, say, 6 to 9 inches above the surface of the ground surrounding it.

When drains outside the stable are required, care should be taken that while they efficiently serve their purpose, no effluvium from them will have any chance of contaminating the air breathed by the horses.

The question of subsoil (covered) drains which open inside the stable is chiefly one of labour. With an exception to which I shall presently allude, they are objectionable; because they tend to render the place unsanitary by the foul gas and damp emitted from them, and because they necessitate a slope being given to the surface upon which the horses stand. A common form of drainage which combines both these disadvantages, is one in which a drain runs down the centre of a line of stalls, into which it opens by means of grates; the floors of the different compartments being made to slope towards their respective grates. Owing to the presence of the horses' litter, especially if peat moss, tan, or sawdust be used, this drain is liable to become blocked up, and when in that condition is more apt than ever to give off unhealthy stenches and vapour. Besides, as the urine will then be unable to escape by means of the drain, it will probably accumulate under the horses. The objection as to contamination of air and flooring by this system of drainage can be more or less removed, if there be a free supply of water, by having, instead of grates, the openings of these drains provided with blocks of stone or other convenient material, so as to keep them hermetically closed, except when it is required to sluice out the drain, on which occasions the blocks can be taken up and afterwards replaced.

There is no actual need of any form of drainage inside the building; for all the urine, dung, etc., can be removed along with the soiled portions of the bedding, as is done in racing and other stables - that of the London Road Car Omnibus Company for instance. The use of peat moss as bedding will greatly facilitate the work of keeping the place clean. Under this system, which is the one I prefer for every kind of horse, the flooring of the stalls and boxes can be made level.

There can be no objection to a small open drain placed along the rear of a line of stalls, so as to carry away fluid. A slope of 1 in. in 5 ft. will suffice for this drain, and a similar slope given to the floors of the stalls will enable them to drain into it. If the stalls thus drained are numerous, and are on the same level, the lower end of the drain will be of a considerable depth, and it may consequently be necessary to provide a portion of it with a covering, so as to enable the horses to go in and out of the stalls without catching their feet in the drain. This covering should be removable for purposes of cleanliness. Drains on this plan are made by manufacturers of stable fittings.

A receptacle for urine in the form of an iron bucket, earthenware pot, or other similar contrivance, placed under a grating in the centre of a box or stall, so as to serve as a substitute for a drain, is such a dirty and unsanitary arrangement, that it should not be allowed in any stable.

Any decided slope - say, more than 1 in 50 - given to the floor of a stall for purposes of drainage is objectionable; because a horse needs for the comfort and health of his feet and legs a more or less level bearing on which to stand. A slope of 1 in. in 5 ft. will be a fair compromise between comfort to the horse and efficiency of drainage. There is less objection to a slope being given to the floor of a loose-box than to that of a stall; for in a box the animal can readily change his position, supposing that he is not tied up; but in a stall he can do so only to a small extent. When the ground upon which a horse stands, rises towards the front, the proportion of weight placed on the hind feet will be greater than if the ground was level; because, in the former case, a perpendicular drawn through the centre of gravity of the animal will be nearer the point of contact of the hind feet with the ground, than in the latter. Supposing - in order to further demonstrate this fact - that the upward slope was so great that this perpendicular passed through the said point of contact; the whole of the weight would be borne by the hind legs, and none by the fore ones. Some erroneously think that when a horse stands on ground which rises to the front, more strain is put on the flexor tendons (back sinews) of the fore legs, than when the horse stands level; because, in the former case, the toes of the fore feet are higher than in the latter. Such persons, however, ignore the fact that the weight borne by the fore feet, and consequently, the strain on the flexor tendons of the fore legs, varies in inverse proportion to the upward inclination of the ground. These conditions are of course reversed when the ground slopes downwards to the front.

Mayhew (Illustrated Horse Management) advocates the use, in stalls, of floors which slope downwards to the front; because, so he says, horses stand with more ease to themselves on ground which slopes in that direction, than on level ground or on ground which slopes to the rear. I have not been able to verify this statement.