What a French Drain Is
A French drain is a gravel-filled trench with a perforated pipe at the bottom, usually wrapped in filter fabric. Water in the surrounding soil moves into the gravel, enters the pipe through the perforations, and flows by gravity to a discharge point away from the problem area.
French drains are subsurface drainage — they're most effective on water moving through the soil, or water that reaches the ground and needs somewhere to go before it becomes a puddle.
When a French Drain Is Usually Considered
- A soggy area that stays wet long after rain
- Water traveling underground from an uphill area
- A wet spot at the base of a slope
- Areas along a foundation where water tends to sit
- Yard sections that never fully dry out during the growing season
How It Generally Works
- A trench is cut along the wet area at a controlled slope
- Filter fabric lines the trench to keep soil out of the gravel
- Washed drainage stone surrounds a perforated pipe
- The pipe carries collected water by gravity to an approved discharge point
- The trench is backfilled and finished at the surface
Why Slope and Discharge Matter
The two things that make or break a French drain are consistent slope and a proper discharge location. Without both, water either sits in the pipe or comes right back up somewhere else. This is why a walk-through of the property matters more than any single spec sheet.
When a French Drain May Not Be the Right Answer
Sometimes the water problem is purely on the surface — a low spot, a yard that slopes the wrong way, or downspouts dumping runoff in one place. In those cases, regrading, downspout extensions, or a catch basin may solve the issue at lower cost and with less disturbance than installing a full French drain.
This is why an on-site assessment matters. The right solution depends on where the water is coming from, where it's going, and what your yard actually looks like.
Weighing whether to dig it yourself? Our DIY vs. Professional Yard Drainage guide walks through what a French drain install really involves and when it's worth calling a pro.