A lateral tile drain should enter a main at an acute angle to prevent too great a check in the current.
In putting in a drainage system the first thing to be done is to make a plan of the ground and determine the slope of the land and the grade of the drain. The ditches are then staked out and the digging proceeds. In digging the ditches plows are sometimes used to throw out the top soil, then the work is finished with spades and shovels.
Professional ditchers use special tools and they take out only sufficient earth to make room for the tiles ([Fig. 85]). The tiles are then laid end to end, the joints covered with a piece of sod, some grass, straw, paper or clay, to prevent loose soil sifting in. As the tiles are laid, enough soil is placed on them to hold them in place until the ditch is filled.
In laying the tiles an even grade should be maintained ([Fig. 86]). A lessening of the grade checks the current of water and tends to cause a stoppage of the drain.
The water gets into the drain through the joints where the tiles come together.
The outlet of a tile drain should be protected by brick work or should be of glazed tile such as the so-called terra-cotta tile, to prevent injury by frost.
The mouth of the drain should be protected by a screen of wire to prevent the entrance of rats and other small animals.