BLOG How to Build a French Drain That Actually Works (And Why Most Fail) Jul 15, 2026

A French drain has one job: collect groundwater and move it somewhere else.

Sounds simple enough.

The problem is that many French drains fail—not because the idea is bad, but because they're built incorrectly. We've excavated countless "French drains" that stopped working after only a few years. Almost every time, the cause is the same: shortcuts during installation.

Recently, we repaired a retaining wall drainage problem where groundwater had nowhere to go. Water was building up behind the wall until it began seeping underneath it and bubbling out of the ground after heavy rains. The homeowner already had a French drain installed—but it wasn't doing its job.

Here's what we found and how we fixed it.

Want to see it instead? Check out the video here: https://youtu.be/sqfHIJqhbCM

Step 1: Find the Real Problem

Before installing anything new, we uncovered the existing drainage system.

Immediately, two major issues became obvious.

First, the French drain wasn't installed at the bottom of the retaining wall. Instead of intercepting groundwater before pressure built up, it was installed too high to capture the water where it naturally collected.

Second, the pipe was extremely shallow. In some places, the sod was sitting directly on top of it. It wouldn't have taken much traffic to damage the system.

Neither problem was visible from the surface.

That's why diagnosing the cause of a drainage problem is just as important as installing the solution.

Step 2: Understand Why Most French Drains Fail

As we continued excavating, we uncovered something we see all the time.

The previous installer had surrounded the pipe with beautiful decorative river rock.

Unfortunately, they skipped one critical component:

Non-woven geotextile filter fabric.

Without filter fabric, soil naturally migrates into the stone over time. Eventually, every void between the rocks fills with dirt until water can no longer move through the system.

What started as a drainage system becomes nothing more than buried gravel.

People often say, "French drains don't work."

In reality, improperly built French drains don't work.

A properly constructed burrito-wrap French drain can function for decades because the filter fabric keeps soil separated from the drainage stone.

Step 3: Dig the Right Trench

Depth matters.

Our trench was approximately 12 inches deep and 10–12 inches wide.

More importantly, the trench was excavated down to where the groundwater actually existed—not simply where it was convenient to dig.

We also removed all excavated soil from around the trench so none of it could accidentally contaminate the clean drainage stone during installation.

Step 4: Keep the Bottom Flat

One mistake DIY installers often make is creating dips and humps in the trench.

Groundwater doesn't need a steep slope.

It simply needs a consistent path to follow.

A smooth, flat trench allows water to move efficiently into the pipe while preventing areas where sediment can accumulate.

Step 5: Build a True Burrito-Wrap French Drain

This is where long-term reliability is built.

The installation sequence is simple:

• Line the trench with non-woven geotextile filter fabric.
• Install clean perforated pipe.
• Transition to solid pipe where groundwater collection ends.
• Surround everything with washed drainage stone.
• Wrap the entire system completely in the filter fabric.

This complete enclosure is what gives the "burrito wrap" its name.

The goal is simple:

Water gets in.

Soil stays out.

Step 8: Install a Critter Guard

One small detail makes a big difference.

Rather than leaving the end of the perforated pipe exposed, we install a purpose-built fitting called a critter guard. This part keeps small animals out of the drain.

Without a critter guard, animals can take up residence during the dry season and create blockages.

Step 9: Overlap the Fabric Correctly

Here's a tip many installation guides never mention.

When wrapping your filter fabric, make sure the uphill side overlaps on top of the downhill side.

Why?

Because soil naturally migrates downhill over time.

If the overlap faces the wrong direction, soil can gradually work its way underneath the flap and into the drainage stone.

Proper overlap acts like shingles on a roof—allowing nature to work with you instead of against you.

Step 10: Restore the Surface

Once the drain is wrapped, we top-dress with clean sand before reinstalling sod.

The sand helps smooth the surface while allowing water to pass freely into the drain.

Just remember:

Sand belongs above the filter fabric—not inside the French drain itself.

The Result

To test the finished system, we ran a hose continuously into the problem area.

Previously, this location would become saturated almost immediately.

Now?

The water entered the French drain, traveled through the system, and exited rapidly at the discharge point without allowing water to build up behind the retaining wall.

That's exactly what a properly built French drain is designed to do.

Final Thoughts

A French drain isn't just a trench with gravel and pipe.

Its success depends on dozens of small installation details:

• Installing at the correct depth.
• Using clean drainage stone.
• Wrapping the system completely in non-woven geotextile.
• Keeping sediment out.
• Providing a proper outlet.
• Building it to last instead of simply making it look finished.

When every component works together, groundwater is collected before it becomes a problem, retaining walls stay dry, and homeowners avoid the expensive repairs that come with trapped water.

At Drain My Lawn, we don't just install French drains—we build systems designed to solve drainage problems for the long haul. If you're in the Charlotte area and dealing with standing water, saturated lawns, or retaining wall drainage issues, we'd be glad to help.