French Drain Pipe Size Guide
When to use 3 inch, 4 inch, or 6 inch perforated pipe in a french drain, and the difference between corrugated and rigid PVC.
4 inch perforated pipe is the standard for residential french drains. Use 3 inch only for short, low-flow runs. Use 6 inch for long runs, multiple downspout tie-ins, or steep grades where flow volume climbs quickly.
By pipe size
- 3 inch: short runs under 20 feet, small bed drainage
- 4 inch: standard residential french drain, up to 100 feet
- 6 inch: long runs, multiple tie-ins, heavy runoff areas
Corrugated vs rigid PVC
Corrugated (black flexible pipe): cheap, easy to bend, but easier to crush and harder to snake. Rigid PVC: costs more, requires fittings at bends, but is far more durable and cleanable. For a foundation drain, use rigid PVC.
Filter sock or fabric?
Wrap the pipe in a filter sock (or the trench in landscape fabric) any time the surrounding soil has silt or fines. Skip only for pure sand or clean gravel backfill.
Ready to run the numbers?
Use the french drain calculator to get a specific quantity for your project.
Open the french drain calculator →Related guides
Last reviewed . Educational estimates only; local conditions and codes take precedence. Consult a qualified professional for site-specific decisions.