French Drain — trench drain that redirects groundwater

A french drain is a gravel-filled drainage trench that collects and redirects subsurface water away from wet areas and foundations.

French Drain diagram — labeled parts, dimensions, and installation context

What It Is

A French drain is a trench filled with gravel, often containing perforated pipe, that intercepts and redirects groundwater. It gives subsurface water an easier path to follow than pooling in the yard or pressing against the foundation.

Types

Common forms include exterior foundation French drains, yard intercept drains, curtain drains on slopes, and interior basement perimeter drains. Some rely mostly on gravel, while others center on perforated pipe.

Where It Is Used

French drains are used along foundations, in wet lawns, around retaining walls, uphill of structures, and anywhere runoff or groundwater tends to collect. They are often part of a larger drainage strategy.

How to Identify One

You may see a gravel strip, a buried trench path, or a visible outlet where collected water discharges downhill or into a sump. Persistent soggy soil above the trench is a common clue.

Replacement

Replacement is needed when the trench silts up, the pipe collapses, roots invade, or the original slope was never adequate. A durable rebuild depends on clean stone, filter fabric, and a reliable outlet.

French Drain — FAQ

What does a french drain do?

It collects and redirects subsurface water away from wet areas and foundations. In a home, that helps the surrounding system work the way it should.

How can I tell if a french drain needs attention?

Standing water, soggy lawns, basement seepage, and outlets that never flow during wet weather can all mean the system is failing. Root intrusion and fine soil clogging are common causes.

Can I replace a french drain myself?

A simple yard French drain is within reach for some homeowners who can manage trenching and slope carefully. Large foundation drains are more disruptive and harder to discharge correctly.

How much does french drain repair or replacement cost?

Small landscape drains can be moderate projects, but long runs, excavation near structures, and difficult discharge routes raise the price quickly. Access and soil volume drive the budget.