French drain INSTALLATION COST

How a French drain system works

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A French drain gives water in wet soil a permeable collection path and a route toward a discharge point. The pipe alone does not solve the problem.

US house and yard cutaway showing the drainage systems outside the house.

How does a French drain system work?

A French drain gives water in wet soil a permeable collection path and a route toward a discharge point. The pipe alone does not solve the problem.

Collection happens below the surface

Water moving through soil can enter the gravel collection zone and the perforated pipe. Fabric and clean aggregate help keep native soil separate from the void space. A grated basin collects surface runoff differently: water must reach its inlet.

Choose collection hardware for the water source rather than calling every buried pipe a French drain.

The outlet completes the system

A gravity system needs a workable elevation relationship from collector to outlet. The route, pipe capacity and discharge conditions must be checked together. A dry well can provide infiltration where soil and groundwater conditions permit it, but it is not a universal substitute for an outlet.

Saturated ground may absorb little additional water.

Keep concentrated roof water separate

A downspout typically feeds solid conveyance pipe. Connecting that concentrated inflow into a perforated collection section can put roof water back into the surrounding ground. PNNL’s building-science guidance separates roof-water drainage from foundation drains.

Ask how the proposal keeps those functions distinct.

Recognize the limits

A collector cannot repair a leaking supply line, change a neighbor’s drainage rights or waterproof a basement wall. Clogging, a blocked outlet, poor elevations or an undersized system may all leave wet ground. Inspect accessible inlets and outlets and have recurring failures assessed before adding more pipe.

Cutaway of a yard French drain trench beside a brick ranch house: fabric-lined trench, gravel and a black perforated pipe under the lawn.
A yard drain in cross-section; outlet suitability needs an on-site check.

Nonwoven fabric keeps soil out of the gravel so the drain doesn't clog.

Washed gravel around the pipe lets water reach it from every side.

Water rises into the holes and runs along the pipe, which slopes toward the outlet.
Questions to ask before work starts
Does the pipe need holes?
The collection section uses perforations; the conveyance section can use solid pipe. Product details and installation orientation must follow the selected system.
Will it drain every puddle immediately?
No. Surface water must reach the collector, and performance depends on soil, storm volume, elevation and outlet capacity.
Sources
Cutaway of a yard French drain trench beside a brick ranch house: fabric-lined trench, gravel and a black perforated pipe under the lawn.

French drain cost

Per-foot prices, worked examples and what changes the total.

US house and yard cut away to show a French drain, downspout line, dry well, catch basin and driveway channel drain.

French drain installation, step by step

What a pro does, from the site check to lawn repair.

Two-story US house with a gravel French drain trench curving through a wet lawn.

French drain for a soggy yard

When a yard drain fixes standing water, and when it won't.