What Is a French Drain?

A French drain is a gravel-filled trench containing a perforated pipe that redirects surface water and groundwater away from an area. It's the most effective solution for yard drainage problems, wet basements, and foundation water issues. The perforated pipe collects water that seeps through the gravel and carries it to a safe discharge point—a storm drain, dry well, or lower area of your property. Despite the name, French drains were popularized by Henry French in 1859 in Massachusetts, not France.

French drains work through gravity and the path of least resistance. The trench is dug with a slight slope (typically 1% grade, or 1 inch drop per 8 feet). Gravel surrounds the perforated pipe, creating an easy path for water to flow. Water naturally moves toward the loose gravel rather than through dense soil. Once in the gravel, water enters the pipe through perforations and flows downhill to the discharge point. Filter fabric wraps the gravel to prevent soil from clogging the system.

Both plumbers and landscapers install French drains, but the right choice depends on your situation. Call a plumber when: the drain connects to existing plumbing, involves foundation waterproofing, or requires permits. Call a landscaper for: simple yard drainage solutions and surface water management. For basement waterproofing or drainage near foundations, a plumber or waterproofing specialist is the better choice—they understand building codes and can integrate with your home's existing drainage.

French drain installation costs $20-$50 per linear foot on average, with most residential projects totaling $1,000-$5,000. Factors affecting cost include: trench depth (deeper = more expensive), soil type (rocky soil costs more to excavate), length of the drain, and discharge location requirements. Interior French drains (basement perimeter systems) cost more—$3,000-$12,000 for a full basement. Get multiple quotes; prices vary significantly between contractors.

Consider a French drain if you have: standing water in your yard after rain, a soggy or perpetually wet lawn area, water seeping into your basement, foundation cracks from water pressure, or downspouts that discharge too close to your foundation. French drains solve drainage problems that grading changes alone can't fix. They're particularly effective for homes at the bottom of slopes or in areas with high water tables.