French drain vs. trench drain
The names get used interchangeably, but they're different systems for different water. A french drain collects water from the soil; a trench (channel) drain catches water running across a hard surface.
| French drain | Trench / channel drain | |
|---|---|---|
| Catches | Subsurface + standing water in soil | Surface runoff on paving |
| Looks like | Gravel-filled trench, perforated pipe, usually buried | Long surface channel with a grate |
| Best for | Soggy yards, wet basements, foundation water, saturated slopes | Driveways, patios, pool decks, garage aprons |
| How water enters | Percolates down through gravel into the pipe | Falls straight into the grated channel |
| Typical cost | ~$20–$40/ft exterior (more interior) | ~$30–$150/ft installed (concrete work) |
Which do you need?
If your problem is a wet lawn, a saturated foundation, or basement seepage, you want a french drain. If water is sheeting across a driveway, patio, or garage floor, you want a trench drain. Many properties end up with both — a trench drain across the driveway that ties into a french drain carrying the water away. A good drainage contractor installs either and will tell you which your site calls for.