A French drain system, otherwise referred to as a sub-floor drainage system or pressure relief system, is a perforated pipe installed below the basement floor slab. The pipe is wrapped in a filter screen and set in a drainage envelope, creating a void that’s less dense than the surrounding soil.
The Importance of a French Drain
A French drain promotes water flow into the pipe. The water moves to a discharge location, which is an automatic submersible sump pump or daylight depending on topography.
A basement is in the ground. Depending on its location and the consistency of the soils, water may be found in the ground where the basement is situated. When eye water rises to an elevation where it comes in contact with the basement floor and foundation walls, the basement will become submersed in water.
If this occurs, hydrostatic pressure will build around the basement. Hydrostatic pressure will then force the water into the basement, creating a flooding, wet condition.
The purpose of a French drain system is to remove the water that is under the basement floor. It dewaters the soils under and around the basement, so it does not become submersed in water.
Removing this fluid will reduce the potential for hydrostatic pressure to build against the basement floors and foundation walls. This reduces the potential for water to enter into the basement and the possibility of a flooding condition. Afterwards, the result is a dry basement to be used for living and storage