(7) French Drains are holes filled with rocks. Period. French drains do NOT contain drainage tile or pipe. French drains do NOT conduct water to other places. French drains are entirely self contained. Many people use the term French drain as a synonym to describe other drainage technologies. This is NOT correct.
John Polk wrote:I beg to differ with you on this point. French drains, as first described by Henry French of Massachusetts in the mid 19th century, did use tiles at their base, and did divert water to other places. The tiles were usually either perforated, or set with gaps to allow some filtration, while carrying the bulk of water to a safe distance. They became quite popular around building foundations, and agriculturally to drain excess water from fields. Most were designed for a slow seep, combined with a slow diversion (usually between 1:100 and 1:200).
A French drain or weeping tile (also blind drain, rubble drain, rock drain, drain tile, perimeter drain, land drain, French ditch, sub-surface drain, sub-soil drain or agricultural drain) is a trench filled with gravel or rock or containing a perforated pipe that redirects surface water and groundwater away from an area. A French drain can have perforated hollow pipes along the bottom (see images) to quickly vent water that seeps down through the upper gravel or rock.
French drains are primarily used to prevent ground and surface water from penetrating or damaging building foundations. Alternatively, French drains may be used to distribute water, such as a septic drain field at the outlet of a typical septic tank sewage treatment system. French drains are also used behind retaining walls to relieve ground water pressure.