French Drain Installation: Send Water Away From Your Home

TL;DR: A French drain redirects water that pools in your yard or against your foundation. Done right, it's a permanent fix — here's how.

_Last reviewed: July 2026 · 3 min read_

A French drain — a gravel-filled trench with a perforated pipe — collects water that pools in your yard or seeps against your foundation and carries it somewhere safe. Done right, it's a permanent drainage fix; done wrong, it clogs or runs backward. Four fundamentals make it work: map the water, slope the trench, line it correctly, and keep the outlet clear.

How do I plan a French drain?

Map where water naturally collects after rain. Watch your yard during a downpour and note where water pools, where it flows, and where it sits against the foundation. The drain has to intercept that water and lead it to a lower spot. Planning the route around how water actually moves on your property is what makes the drain effective — it's the same instinct behind basement waterproofing.

Why does the slope matter so much?

Everything — dig the trench with a consistent downward slope toward the outlet, generally about 1% (roughly 1 inch of drop per 8–10 feet). Water moves by gravity, so a flat or uneven trench just holds water instead of draining it. Use a level and string line as you dig to keep a steady fall the whole way. Slope is the single most important detail.

How do I line a French drain trench?

Line the trench with landscape fabric and gravel. Lay water-permeable fabric in the trench (it keeps soil and roots from clogging the system), add a gravel base, set the perforated pipe (holes down is the common method for groundwater collection), surround it with gravel, then wrap the fabric over the top before backfilling. The fabric-and-gravel envelope is what keeps the drain flowing for decades instead of silting up.

Why must the drain outlet stay clear?

Make sure the drain outlet is clear and unblocked — the whole system fails if the water has nowhere to exit. The outlet should daylight at a lower point, a dry well, or a storm drain (per local rules), and stay free of debris, soil, and critters (a grate helps). Check it periodically, especially after storms. A blocked outlet backs the whole drain up, undoing all the work.

Track drainage projects

Logging your drainage work and any wet spots helps you manage water long-term. Okoniq Property Hub keeps it with your home maintenance records in one private place. Pair it with foundation crack monitoring.

Frequently asked questions

Do I need to call before digging a French drain?

Yes — call 811 (in the U.S.) to have underground utilities marked before you dig. Hitting a buried line is dangerous and expensive. This is a must before any trenching project.

When should I hire a pro for a French drain?

For drains tied to serious foundation water, long runs, hard digging, or where slope and outlet are tricky, a drainage contractor is worth it. Short yard drains are a doable (if labor-intensive) DIY with careful slope.

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FAQ

How much does it cost to install a French drain?

A professionally installed French drain typically costs $20 to $50 per linear foot, depending on depth, soil conditions, and whether you're working near a foundation or just in open yard. A DIY shallow yard drain can run $5 to $10 per foot in materials (gravel, pipe, fabric), but factor in tool rental and the labor to dig and grade the trench correctly.

How long does a French drain last?

A properly installed French drain with landscape fabric and clean gravel can last 30 to 40 years or more. The key is keeping the outlet clear and making sure the fabric was wrapped correctly at installation — drains fail early when soil migrates into the gravel or roots invade the pipe.

Can a French drain freeze and stop working in winter?

Yes, in very cold climates the water in the pipe can freeze temporarily and slow drainage, but the drain usually thaws and resumes flow once temperatures rise. To minimize risk, make sure the outlet daylights above the frost line and slopes sharply so water doesn't sit in the pipe. Most French drains still function through mild winters without issue.

What's the difference between a French drain and a curtain drain?

A French drain is the general term for any gravel-and-pipe trench that moves groundwater. A curtain drain is a specific type installed upslope of a foundation to intercept water before it reaches the house — it "curtains off" the foundation. Both use the same construction method; the difference is placement and purpose.