What this covers
A French drain is a trench with perforated pipe set in washed gravel and wrapped in filter fabric that collects water from the soil and carries it to a lower point, a dry well or a storm drain. The company lays out the run with a steady fall, digs the trench, lines it with fabric, beds the pipe with the holes facing down, backfills with gravel and finishes with soil and sod or a gravel strip. Yard drains collect surface water in a soggy lawn; footing drains along a foundation pick up water before it reaches the wall. The outlet matters as much as the trench: the water has to have somewhere to go.
When to call
- A section of lawn that stays soggy for days after rain.
- Water running toward the house from a neighbor's yard or a slope.
- A patio, walkway or driveway that pools and sheets toward the foundation.
- Downspouts that dump beside the foundation with nowhere to drain.
What to expect
- Lay outThe low points, the fall of the trench and the outlet are set with a level or laser.
- Dig and lineThe trench is dug to grade and lined with filter fabric.
- Pipe and gravelPerforated pipe is set on a gravel bed, covered with gravel and the fabric folded over.
- FinishThe trench is topped with soil and sod or left as a gravel strip, and the outlet is checked in rain.
Get a certified company
Look up a certified company by ZIP code. Every company's license, insurance and trades are verified before it is listed, and placement is never paid.
Questions people ask
What slope does the pipe need?
A minimum of about one percent, or one inch of fall over eight feet, so water moves rather than sits. The outlet has to be lower than the whole run.
Holes up or down?
Down. Water fills the gravel from below and enters the pipe through the bottom holes, and the pipe stays clear of fine soil longer. Fabric around the gravel, not the pipe, keeps the silt out.
Can downspouts tie into a French drain?
Downspouts carry a lot of water quickly and are better run in a separate solid pipe to the same outlet. Tying them into a perforated drain can flood the trench and push water into the soil it is meant to drain.
Related: Yard grading and drainage · Basement waterproofing · Gutter installation · All foundation, basement and drainage
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