A footing drain (often mistakenly called a French drain) is a perforated pipe set in porous fill (clean gravel) that is placed at the level of the footing all the way around the building. It slopes slightly downward toward an “outfall” downhill from the building or a sump. A footing drain’s purpose is to gather water that seeps through the ground and conduct it away from the basement or foundation wall before it can penetrate the wall. It is a critical part of keeping a basement dry. The footing drain must be wrapped in geotextile fabric to prevent silt from entering the pipe and clogging it up. Don’t expect gushes of water to come out of these drain pipes. The water they lead away from the foundation is just seeping and trickling water.
If a house is in a location that has a seasonally high water table, it is a good idea to install an additional footing drain under the basement slab on the interior side of the footing. Also, be sure to install good waterproofing on the foundation walls and grade the surface of the ground around the building to slope away from the house. A footing drain cannot keep your basement dry if you have poor waterproofing and rain puddles against the basement walls.