What Is a French Drain?
A French drain is a gravel-filled trench with a perforated pipe inside, sloped to carry subsurface water away from a problem area to a safe outlet — typically a daylight point at the property edge, a dry well, or a connection to the storm sewer. The gravel allows water to enter the trench from all sides; gravity and the pipe move it toward the outlet.
Despite the name, it has nothing to do with France. Henry French was a Massachusetts judge who documented the method in his 1859 farming manual. The underlying physics haven't changed since: water flows downhill, and a well-graded path will collect it reliably for decades with almost no maintenance.
Signs You Actually Need One
Not every wet area needs a French drain. Surface grading fixes — regrading low spots, redirecting downspouts, extending leaders — solve the majority of yard drainage problems at lower cost. A French drain is the right tool when water is coming up through the soil rather than pooling from surface runoff. These symptoms point to a subsurface drainage problem:
- Standing water that persists 24–48 hours after rain has fully stopped
- Chronically soggy, spongy turf in the same location every spring
- Dead grass or persistent moss where drainage is always poor
- Water seeping into a basement or crawl space during or after heavy rain
- Mulch beds that never fully dry out and smell of sulfur or rot
- Retaining walls that lean, bulge, or show white efflorescence (a sign water is moving through the wall structure)
How We Design and Route Them
The most critical element is the outlet. Water moved away from a problem spot has to go somewhere — ideally to daylight on a downhill slope, where it discharges onto grass or a stone splash pad. Connecting to the municipal storm sewer requires confirming local ordinances and sometimes obtaining a permit; not all municipalities allow private connections.
Minimum slope is 1% — one inch of drop per 100 linear inches of pipe. In practice we aim for closer to 1.5–2% where the grade allows it. Flatter than 1% and sediment gradually builds up in the pipe; steeper and the system moves water faster and self-cleans.
We wrap the perforated pipe in a non-woven geotextile sock and line the trench with filter fabric before filling with washed drainage stone. This is the step most homeowners skip on DIY installs — and it's why those systems silt up within five to ten years. The fabric keeps clay fines out of the gravel, and the gravel keeps the pipe from crushing under soil load.
DIY vs. Professional Install
A French drain across a flat, accessible lawn with a clear downhill outlet is a manageable DIY project if you have access to a trencher and understand basic grading. A drain routing around a foundation, through an established landscape, or across a clay-heavy backyard with no obvious outlet is not — the excavation requires real equipment, and routing errors can push the drainage problem onto a neighboring property or, worse, toward the foundation instead of away from it.
Before any digging, call 811 to have underground utilities located. It's free, legally required in Ohio, and takes two business days. Gas lines, buried electric, and fiber optic runs are more common than most homeowners expect — and far more expensive to repair than the drain itself.
What to Do After It's Installed
A properly built French drain with filter fabric and clean drainage stone should function for 20–30 years without significant intervention. Basic annual checks:
- Clear the outlet end of leaf debris and sediment each spring before the wet season starts
- Run a hose into the inlet cleanout (if one was installed) and confirm water exits at the outlet within a reasonable time
- Watch for new surface settling or slight sinkholes along the trench line — they may indicate a joint separation in the pipe
Avoid planting trees within five feet of any drain line. Root intrusion is the leading cause of premature French drain failure — roots find the perforated pipe and grow into it over time, collapsing flow. We note drain locations in our project records so future landscape work doesn't inadvertently plant over them.
