Farm drainage / The Principles, Processes, and Effects of Draining Land with Stones, Wood, Plows, and Open Ditches, and Especially with Tiles

by Henry F. French

Obstruction by Filling at the Joints. One would suppose that tiles might frequently be prevented from receiving water, by the filling up of the crevices between them. If water poured on to tiles in a stream, it would be likely to carry into these openings enough earthy matter to fill them; but the whole theory of thorough-drainage rests upon the idea of slow percolation—of the passage of water in the form of fine dew, as it were—through the motionless particles which compose the soil; and, if drains are properly laid, there can be no motion of particles of earth, either into or towards the tiles. The water should soak through the ground precisely as it does through a wet cloth.

In an article in the Journal of the Society of Arts, published in 1855, Mr. Thomas Arkell states that in 1846 he had drained a few acres with 1¼ inch pipes, about three feet deep, and 21 to 25 feet apart. The drains acted well, and the land was tolerably dry and healthy for the first few years; but afterwards, in wet seasons, it was very wet, and appeared full of water, like undrained land, although at the time all the drains were running, but very slowly. His conclusion was that mud had entered the crevices, and stopped the water out. He says he has known other persons, who had used small pipes, who had suffered in the same way. There are many persons still in England, who are so apprehensive on this point, that they continue to use horse-shoe tiles, or, as they are sometimes called, "tops and bottoms," which admit water more freely along the joints.

The most skillful engineers, however, decidedly prefer round pipes, but recommend that none smaller than one-and-a-half-inch be used, and prefer two-inch to any smaller size. The circumference of a two-inch pipe is not far from nine inches, while that of a one-inch pipe, of common thickness, is about half that, so that the opening is twice as extensive in the two-inch, pipes as in the one-inch pipe.

The ascertained instances of the obstruction of pipes, by excluding the water from the joints, are very few. No doubt that clay, puddled in upon the tiles when laid, might have this effect; but they who have experience in tile-drainage, will bear witness that there is far more difficulty in excluding sand and mud, than there is in admitting water.

It is thought, by some persons, that sufficient water to drain land may be admitted through the pores of the tiles. We have no such faith. The opinion of Mr. Parkes, that about 500 times as much water enters at the crevices between each pair of tiles, as is absorbed through the tiles themselves, we think to be far nearer the truth.

Collars have a great tendency to prevent the closing up of the crevices between tiles; but injuries to drains laid at proper depths, with two-inch pipes, even without collars, must be very rare. Indeed, no single case of a drain obstructed in this way, when laid four feet deep, has yet come within our reading or observation, and it is rather as a possible, than even a probable, cause of failure, that it has been mentioned.

HOW TO DETECT OBSTRUCTIONS IN DRAINS.

When a drain is entirely obstructed, if there is a considerable flow of water, and the ground is much descending, the water will at once press through the joints of the pipes, and show itself at the surface. By thrusting down a bar along the course of the drain, the place of the obstruction will be readily determined; for the water will, at the point of greatest pressure, burst up in the hole made by the bar, like a spring, while below the point of obstruction, there will be no upward pressure of the water, and above it, the pressure will be less the farther we go.

The point being determined, it is the work of but few minutes to dig down upon the drain, remove carefully a few pipes, and take out the frog, or mouse, or the broken tile, if such be the cause of the difficulty. If silt or earth has caused the obstruction, it is probably because of a depression in the line of the drain, or a defect in some junction with other drains, and this may require the taking up of more or less of the pipes.

If there be but little fall in the drains, the obstruction will not be so readily found; but the effect of the water will soon be observed at the surface, both in keeping the soil wet, and in chilling the vegetation upon it. If proper peep-holes have been provided, the place of any obstruction may readily be determined, at a glance into them.