A french drain that’s doing its job is invisible. You find out it has failed the same way you found out you needed one: the soggy stripe reappears across the lawn, water stands on top of the gravel line for a day after every storm, or the crawl space smells damp again after two dry winters. If that’s where you are, you may not need a whole new system. You need someone to find out where this one broke.
Repairing drains other people installed is a big share of our work around Knoxville. Sometimes the fix is an afternoon with a jetter. Sometimes the honest answer is that the drain was never built to survive East Tennessee clay, and the money belongs in a rebuild instead. We’ll tell you which situation you’re in before you spend anything — the estimate is free.
First, confirm the drain has actually failed
Not every wet yard with a french drain in it is a failed french drain. The quickest test costs nothing: during a hard rain — and with roughly 50 inches falling on Knoxville in a typical year, you won’t wait long — go look at the discharge point.
If the outlet is running strong and the yard is still wet, the drain is working but it’s the wrong tool for the water you have. Surface water pooling in a low spot doesn’t obediently sink down to a buried pipe; that problem usually wants a catch basin or a grading fix instead. If the outlet is dry or trickling while the trench line ponds, water is entering the system and not leaving it — that’s a blockage. And if runoff seems to skip over the drain entirely, the drain may be too shallow or simply in the wrong place to intercept the flow.
We walk through exactly this on the first visit. Which failure you have decides everything about the fix, so we don’t guess at it.
What actually kills french drains here
Silt is the number one killer, and East Tennessee red clay is why. Clay breaks down into fines — particles small enough to ride water through gravel and into the pipe, where they settle and slowly close it off. A drain built without filter fabric has no defense, and corrugated pipe makes it worse: every ridge inside that pipe is a shelf for sediment to build on. We dig out drains in Halls and Karns that silted solid in under five years.
Roots come second. Perforated pipe is a water source, and tree roots treat it like one. A maple or willow within reach will find the perforations, and once inside, roots mat into a plug that snags everything else coming down the line.
Then there’s crushing. Flexible corrugated pipe flattens under a driveway crossing, under equipment, sometimes under nothing more than years of soil weight. One flattened section chokes the entire run behind it.
Some drains never worked at all, because they never had slope. Knoxville’s ridge-and-valley lots tempt installers to follow the terrain, and if any stretch of pipe runs flat or uphill, water sits in it and drops its sediment right there. A drain with no fall isn’t clogged — it’s a buried trough.
The last one is almost embarrassing: a blocked outlet. Mulch piled over the discharge, a stuck pop-up emitter, a critter nest, a landscaper who buried the daylight point. It’s the cheapest fix on this list, so it’s the first thing we check.
Diagnosis without tearing up the yard
Where the pipe allows it, a sewer camera tells us in an hour what a day of digging would. We run it from the outlet or a cleanout, find the blockage or the break, and mark its position on the surface — so if excavation is needed, it’s one targeted hole instead of re-trenching the whole line. Jetting sometimes does double duty here: high-pressure water that scours silt out of rigid pipe can restore a drain in a single visit, and what washes out of the pipe tells us exactly what went wrong inside it.
We’re equally honest about when the camera doesn’t earn its keep. A collapsed corrugated run won’t pass a camera head, and when the symptoms already point to a dead system, a couple of test holes give a faster, cheaper answer. Diagnosis should cost less than the repair — not compete with it.
Repair or rebuild — how we make the call
Repair wins when the drain has good bones. Rigid PVC with a silt clog gets jetted clean. A single crushed section gets cut out and spliced. Root intrusion at one joint gets cleared, and the joint sealed or rerouted. A buried outlet gets re-established, usually with a cleanout added so the next checkup takes five minutes instead of a service call.
Rebuild wins when the failure is the design itself. Corrugated pipe silted along its full length can’t be jetted back to health — the ridges re-trap sediment as fast as it moves. A drain with no filter fabric in clay soil will re-clog no matter how thoroughly we clean it; the soil guarantees it. And a drain laid without fall can’t be repaired into having slope — the pipe is at the wrong elevation, full stop. In those cases we price a proper french drain installation and salvage whatever’s genuinely reusable: an existing discharge line, a sound outlet, sometimes the trench route itself.
In older neighborhoods like Fountain City we’re seeing a wave of 1990s and 2000s corrugated-era installs reach the end of the line at the same time. If yours is one of them, the repair-versus-rebuild math is worth running before spending on either.
What repair costs
Jetting and outlet cleanouts sit at the cheap end — most run a few hundred dollars. Excavated repairs — splicing a crushed length, clearing and sealing a root-invaded joint, rebuilding one failed stretch — mostly land between $500 and $2,500, driven by depth, equipment access, and how much lawn or landscaping has to go back afterward. A full rebuild is priced like new work, typically $25 to $60 per linear foot; our french drain cost guide breaks that down in detail. Every job gets a fixed quote after we’ve walked the yard, and the estimate costs nothing.
Don’t pay for the same drain twice
The worst outcome isn’t a failed drain — it’s paying to clean a drain that was always going to re-clog, then paying again. Call us or send the quote form and we’ll find the actual failure, show it to you, and give you one straight price for the fix that holds. Free estimates across Knoxville and the surrounding area, from Lenoir City to Halls.