Why Is My French Drain Not Working?
The usual reasons a French drain disappoints, how to tell which one applies, and what the fix looks like.
Common Causes
Seven Reasons a French Drain Fails
It's clogged with silt
Drains built without filter fabric, or with flexible corrugated pipe, can fill with fine clay and stop moving water.
The slope is wrong
If any part of the run is flat or slopes the wrong way, water sits instead of flowing out.
The outlet is blocked or buried
A drain is only as good as where it ends. Outlets get buried, crushed, or clogged with roots and debris.
Roof water was tied in
Downspouts connected to the drain can overload it in a storm and clog it with debris.
It's in the wrong place or too shallow
A drain that doesn't intercept where the water actually travels won't catch it.
The pipe is crushed or separated
Heavy equipment, roots, or settling can damage the line underground.
It was the wrong tool
If the water is running across the surface, a surface drain, catch basin, or regrade may be what's needed, not a buried drain.
Diagnose It
How to Narrow Down the Cause
- Watch the yard during a heavy rain: does water pool in the same places, and does anything flow from the outlet?
- Find the outlet: is it visible, open, and flowing, or buried and blocked?
- Look for the cleanout or inspection ports, if the drain has them, and note whether they hold standing water
- Check whether downspouts feed into the drain
- Ask a contractor to run a camera through the pipe to see blockages, crushed sections, and slope problems
Fixes
What Repair Usually Involves
The fix depends on the cause: cleaning or flushing a clogged but sound line, reopening or extending the outlet, separating downspouts, adding a catch basin or regrading where surface water is the real problem, or replacing the damaged or poorly built section.
A French drain that never worked often points to how it was built, not bad luck. Get a written diagnosis before paying for a repair.
Related
Keep Reading
- How a lasting French drain is built
- Downspouts and catch basins
- Yard grading
- French drain cost guide
Drain not doing its job?
Describe what you're seeing in the form below. If it helps, the contractor may ask you to text photos when they call, so keep a few handy.
FAQ
Common Questions
Do French drains work in clay soil?
Do French drains work in clay soil?
They can. Clay drains slowly, so water pools; a gravel-filled trench gives that water an easy path to a pipe. They work best when the slope, materials, and outlet are right, and when the water problem is actually in the soil rather than on the surface.
How can I tell if my French drain is clogged?
How can I tell if my French drain is clogged?
Warning signs are water that still pools in the same spots after storms, little or no flow at the outlet during heavy rain, and soggy ground along the drain's path. A contractor can run a camera through the pipe to see inside it.
Can a clogged French drain be fixed?
Can a clogged French drain be fixed?
Sometimes. Flushing or cleaning can help if the pipe is intact and has a proper slope. If the pipe is crushed, flat, or full of silt from a build without filter fabric, partial or full replacement may be the realistic fix.
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