How to Make A French Drain: The earliest forms of French drains were ditches, pitched from a high area to a lower one and filled with gravel. By filing the ditch with water it allowed them to control the flow rate. These were not called “French Drains” until they were described and popularized by Henry Flagg French in his 1859 book Farm Drainage. French’s own drains were made of sections of ordinary roofing tile laid with a 1⁄8 in (0.32 cm) gap left in between the sections to admit water. Later, specialized drain tiles were designed with perforations. To prevent clogging, the gravel size varied from coarse at the center to fine at the outside and was designed based on the gradation of the soil surrounding the drain. The particle sizing was critical to keep the surrounding soil from washing into the voids in the gravel and clogging the drain. The development of geotextiles (Weed Mat Etc..) greatly simplified this procedure.
French drains continue to be used as a natural way to disperse and/or re-route water run-off. A common use for French drains is to re-direct water away from a structures foundation where excess moisture threatens to damage it. Ideally a French drain would re-direct water to a leach field in an out-of-the-way area with sandy soil, through which the water could percolate.