How to Install a French Drain (+ Cost)

A soggy lawn, a flooded basement, or a perpetually muddy low spot usually points to one fix: a French drain. This buried gravel-and-pipe channel quietly redirects water away from where you don’t want it and carries it to a safe outlet downhill. Below you’ll find a complete step-by-step install, the materials you need, and honest DIY versus pro cost numbers so you can decide how far to take it yourself.

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What a French drain is and when you need one

A French drain is a gravel-filled trench with a perforated pipe at the bottom. Water in the surrounding soil seeps into the gravel, drips through slots in the pipe, and flows by gravity to a lower outlet. There’s no pump and no power required; the whole system works on slope alone. The name has nothing to do with France either, it’s named for Henry French, a 19th-century Massachusetts farmer who popularized the design.

You likely need one if you’re seeing any of these signs. A French drain solves a real water-movement problem, but it won’t fix a clogged gutter or a grading mistake on its own, so diagnose the source first. For a broader look at standing-water problems, see our guide on how to fix yard drainage.

Common signs you need a French drain

• A low spot in the yard that stays soggy for days after rain
• Water pooling against the foundation or seeping into a basement
• A soggy lawn or moss-covered patches that never dry out
• Water running downhill from a neighbor’s property onto yours
• Erosion channels cutting across beds or the lawn after storms

If the water is coming off your roof rather than out of the ground, capturing it at the downspout may be a cheaper first move. Compare options in our roundup of the best rain barrels before you start digging.

Plan the route, the slope, and call 811 first

Good planning is what separates a drain that works for 20 years from one that backs up the first wet season. Before any shovel touches dirt, you need to settle three things: where the water starts, where it can safely go, and what’s buried in between.

Call 811 before you dig

This is non-negotiable and free. Call 811 or submit a request at call811.com at least a few business days before you plan to dig. Utility companies will come mark the location of buried gas, electric, water, and communication lines with paint and flags. Hitting an unmarked line can be fatal and will cost you thousands. Most states legally require the call, so don’t skip it even for a shallow trench.

Map the route and set the slope

1. Identify the wettest point (the inlet) and the lowest safe discharge point (the outlet).
2. Mark the trench path between them with spray paint or a garden hose, keeping it away from trees and structures where possible.
3. Confirm the path drops continuously. You need at least a 1% grade, which is 1 inch of fall for every 8 to 10 feet of run.
4. Drive stakes at the ends, tie a string line between them, and check fall with a line level. Adjust until the string drops at least 1 inch per 8 to 10 feet from inlet to outlet.

If your yard is flat and you can’t reach a daylight outlet, you’ll need to dig deeper toward the outlet to manufacture slope, or plan for a dry well (covered below). Never run a drain uphill, water won’t climb it.

Materials and tools you’ll need

A standard residential French drain uses a short, predictable parts list. Buy the rigid or coiled perforated pipe in the diameter that matches your water volume; 4-inch is standard for most yards.

• Perforated drain pipe (4-inch, with or without a pre-attached sock) — shop perforated drain pipe
• Washed drainage gravel (3/4-inch clean stone, no fines), typically ordered by the cubic yard
• Landscape drainage fabric (non-woven geotextile) to wrap the trench — shop landscape drainage fabric
• An all-in-one option if you’d rather not source parts separately — browse a French drain kit
• Trenching shovel, mattock, and a flat spade
• Wheelbarrow, hand tamper, line level, stakes, and string
• A catch basin or grate inlet if you’re collecting surface water

Always use washed, angular gravel. Pea gravel and “dirty” stone with sand or fines mixed in will clog the system over time. The geotextile fabric is what keeps surrounding soil from migrating into the gravel, so don’t treat it as optional.

Step-by-step French drain installation

With your route marked, utilities flagged, and materials staged, the install itself is straightforward but physical. Plan a weekend for a typical 30 to 50 foot run dug by hand, or rent a trencher to cut the time dramatically.

1. Dig the trench. Aim for 6 to 12 inches wide and 18 to 24 inches deep, maintaining your continuous 1% downhill slope. Check the slope with your string line as you go, deepening toward the outlet, not the inlet.
2. Grade and smooth the bottom. Remove rocks and roots, then verify the fall one more time. A clean, consistently sloped trench bottom is the single most important detail.
3. Line the trench with fabric. Roll non-woven geotextile fabric along the trench so it lines the bottom and both walls, with plenty of overhang on each side to fold over the top later.
4. Add a gravel base. Pour 2 to 3 inches of washed gravel over the fabric and rake it level to create a bed for the pipe.
5. Lay the perforated pipe. Place the pipe on the gravel with the holes facing down (counterintuitive, but it lets water enter low and keeps the pipe draining). Keep it on grade and connect sections per the manufacturer.
6. Backfill with gravel. Surround and cover the pipe with washed gravel up to a few inches below grade, leaving room for the soil or sod cap.
7. Wrap the fabric. Fold the overhanging fabric flaps over the top of the gravel to fully encase it like a burrito. This is your clog protection.
8. Cap the trench. Top with a few inches of soil and sod, or finish with decorative stone for a visible drain. Tamp lightly and grade so surface water still sheds toward the trench.

If you want the drain to also collect surface water, leave the gravel exposed at the top (a “French drain” with a stone cap) or add catch-basin grates along the run rather than capping with soil.

Where does the water go? Daylight vs. dry well

A French drain is only as good as its outlet. You have two main choices, and the right one depends entirely on whether you have downhill grade to work with.

Daylight outlet

The simplest and most reliable outlet. The pipe “daylights,” meaning it exits at the surface somewhere lower than the inlet, such as a ditch, swale, or the low edge of your property. Cap the exit with an animal-proof grate so critters can’t nest inside. If you have the slope, this is almost always the better option because it can’t fill up.

Dry well

When there’s no lower spot to daylight to, the pipe feeds into a dry well: a large buried pit or perforated barrel filled with gravel that holds water and lets it soak slowly into the surrounding soil. Dry wells work best in well-draining sandy soils and need to be sized for your rainfall. In heavy clay, a dry well can simply fill and stay full, so test your soil’s percolation before committing. Keep the well at least 10 feet from your foundation.

Check local codes before discharging onto a neighbor’s land or into a storm system; many municipalities regulate where drainage water can go.

Common mistakes to avoid

• Not enough slope. Less than 1% grade and the water sits in the pipe instead of moving.
• Skipping the fabric. Soil and silt clog the gravel within a few seasons, and the drain dies.
• Using the wrong gravel. Pea gravel or stone with fines packs tight and stops draining. Use washed angular stone.
• Pipe holes facing up. Holes should face down so water enters at the lowest point.
• No real outlet. A drain that doesn’t go anywhere lower just relocates the puddle underground.
• Digging without calling 811. Dangerous, illegal in most states, and expensive if you hit a line.
• Routing too close to trees. Roots will eventually invade and crush the pipe.

French drain cost: DIY vs. pro

Cost is usually quoted per linear foot. Doing it yourself, your spend is mostly gravel, pipe, fabric, and tool rental, which lands around $10 to $25 per foot. Hiring a pro adds labor, equipment, disposal, and permits, typically $20 to $40+ per foot, and more for deep trenches, rocky soil, or interior basement systems.

Renting a trencher (roughly $100 to $200 per day) can pay for itself on longer runs by saving hours of hand-digging. Don’t forget to budget for gravel delivery, which is often the single biggest material line item.

When to hire a drainage pro

A simple surface or shallow yard drain is well within reach for a fit DIYer with a weekend. Bring in a professional when the stakes or the difficulty climb.

• Water is entering your basement or threatening the foundation
• The trench needs to run deeper than about 2 feet or under hardscape
• Your soil is heavy clay or full of rock and won’t perc
• You have no obvious outlet and need a dry well sized correctly
• The drainage problem spans the whole property or involves grading
• Permits or municipal stormwater rules are involved

A pro brings the right equipment, reads your grade accurately, and warranties the work. For the bigger picture on creating a comfortable, water-smart yard, see our pillar guide on outdoor living and backyard landscaping.

Frequently asked questions