Drain tile: what it is, and how it clogs
The name is a leftover from clay pipe. What it describes is the plumbing that decides whether groundwater reaches your floor.
"Drain tile" is one of those trade terms that survives long after the thing it named disappeared. It once meant short lengths of clay tile laid end to end; today it means perforated plastic pipe. The job has not changed: intercept groundwater at the level of the footing and give it somewhere to go that isn't your floor.
How it is supposed to work
The pipe sits at or just below the footing, surrounded by washed stone. Water in the soil moves through the stone far more easily than through surrounding soil, reaches the pipe through its perforations, and runs by gravity to a low point — either daylight on a sloping site, or a sump pit where a pump lifts it out.
Two details make or break it. The washed stone matters because it keeps a clear, high-capacity path around the pipe; stone with fines in it packs down and stops draining. And filter fabric matters because it keeps soil out of the stone. Both are invisible once backfilled, which is exactly why quality of installation is difficult to judge after the fact.
Exterior and interior are not the same system
Exterior drain tile is installed outside the footing, usually at the time the house is built, and intercepts water before it reaches the wall. When a house has drainage problems decades later, this is frequently the thing that has failed — and it is buried under the yard.
Interior drain tile is retrofitted inside: the slab edge is cut, pipe is laid at the footing, and it drains to a sump. It is the practical option in an existing house precisely because it doesn't require excavating outside.
How it clogs, which is the part nobody mentions
A drainage system is a pipe with holes in it, buried in the ground, carrying water that has been through soil. Over decades, predictable things happen.
Silt. Fine soil migrates into the stone and eventually into the pipe. This is the ordinary aging process of exterior drainage, and it is why an original system may simply have stopped working rather than been done badly.
Iron ochre. In some soils, iron-bearing groundwater plus bacteria produces a reddish, gelatinous deposit that coats and blocks perforations. It is regional, it is persistent, and it turns drainage into a maintenance item rather than a one-time install.
Roots. Pipe carrying water is exactly what roots grow toward, and perforations are an invitation.
Crushing or settlement. A pipe that has been damaged during later work, or that has settled out of its intended fall, stops moving water even if it is otherwise clear.
Signs the drainage has stopped working
The symptom is usually not dramatic — it is a basement that has slowly become wetter than it used to be. A sump that used to run occasionally and now barely runs during heavy rain can mean water is no longer reaching it. So can seepage appearing at the cove joint in a house that never had it. Neither is proof, but both are worth noticing.
What can be done about it
Interior systems are often built with access points precisely so they can be inspected and flushed, which is the strongest practical argument for them: a system you can service will outlive one you cannot. Cleaning is specialist work involving cameras and jetting equipment — this is not a job to attempt with a garden hose, which at best moves the silt further along and at worst floods the very space you are protecting.
Exterior drain tile is a harder story. Assessing it usually means excavating, which puts you back in the same decision as a full exterior waterproofing job.
And the first thing worth checking costs nothing: whether the water reaching that drainage is unnecessary in the first place. A downspout discharging at the foundation is loading the drainage system with roof water it was never meant to handle.
Frequently asked questions
Is drain tile the same as a French drain?
They are close relatives — both are perforated pipe in stone. In common usage, drain tile refers to the pipe at a building's footing, while a French drain more often describes a trench used to move surface or yard water somewhere else.
How long does drain tile last?
There isn't a fixed lifespan, because what ends it is silting and site conditions rather than the pipe wearing out. Iron ochre soils are hardest on it. Systems with cleanouts can be maintained; buried exterior ones usually can't.
Can I flush it myself with a hose?
Not sensibly. Without the right equipment you tend to push silt further into the system, and you are introducing water into a system you already suspect isn't draining. This is camera-and-jetting work.
My sump runs less than it used to. Is that good news?
It might be, or it might mean water is no longer reaching the pit because the drainage has silted up. Read it alongside whether the basement is drier or damper than it used to be.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.