A French drain consists of a perforated pipe installed in pea gravel (to keep sediment out of the pipe) in a trench. Water collects in the pipe and is redirected away from the primary location. French drains are used to remediate water issues in or around the exterior of a crawl space or basement. Not addressing water in or around the exterior of a basement can lead to structural damage to the foundation and to mold growth in the basement’s interior. The cost to install a French drain is between $500-$18,000 depending on the type of water remediation system required, with most systems costing an average of approximately $5,000. Factors that impact the cost of a French drain include material used for the drain, permits, installation labor, size, length and dept of the systems, and sump pump requirements. Learn about French drain system requirements and costs for installation.