A French drain, which may also be called a curtain drain, perimeter drain, weeping tile, or agricultural drain, is a gravel-filled trench that includes a perforated or slotted pipe. These drains are used to direct surface water or groundwater away from a specific area, which is usually your home’s foundation. French drains direct surface level water toward the lowest point and allows it to seep through the surface level gravel into the drain. This gravel also blocks the passage of excess debris. The water is then collected in the perforated pipe, running toward the base of the drain and then directed away from your home or toward a more suitable area.
French drains differ from a typical surface drain or gutter system because they collect water, that normally would pool in your yard, over the entire length of the drain instead of one particular spot. They also prevent water from collecting and pooling in specific areas, saturating the ground soil below, and also may lead to foundation problems on the surface or below your home.
Instead, the water is directed to a more desirable location such as a dry well or an area of your choosing. Subsurface drainage systems have been in use for centuries, helping with everything from controlling agricultural runoff to providing yard drainage. They take many forms but are all similar in design and function to the traditional French drain system.
The earliest French drains were simple ditches filled with gravel. While many people assume the origins of the French drain date back to France, the drain’s name is actually believed to have come from a former lawyer and U.S. Assistant Treasury Secretary Henry Flagg French, who marketed them in his 1859 book, Farm Drainage.”