Reviewed by the Waterproofing Service Editorial Team. Last reviewed: July 30, 2026. This is an independent educational resource; it is not affiliated with, and does not promote, any specific contractor. See Sources below for citations.
A French drain is a simple, decades-old drainage concept: a trench filled with gravel around a perforated pipe, designed to collect groundwater and carry it away before it can build up pressure against a foundation. In Canada, the same basic system around a foundation’s footing is usually called a weeping tile, though the terms are often used interchangeably.
How It Works
A perforated pipe sits at the bottom of a trench, surrounded by coarse gravel. The gravel acts as a filter: it lets water through while keeping most soil particles from clogging the pipe (the pipe itself is often wrapped in a fabric sock for extra filtration). Water that would otherwise saturate the soil against a foundation instead drains into the pipe and is carried away, either to a storm sewer, a dry well, daylight down a slope, or into a sump pit for pumping.
Interior vs. Exterior Placement
- Exterior placement (installed alongside the foundation footing, outside the wall) intercepts groundwater before it reaches the wall at all. This is generally the more effective approach for preventing pressure from building up in the first place, but it requires excavation around the perimeter of the house.
- Interior placement (installed along the inside edge of the basement floor) manages water after it has already reached the foundation, typically channeling it to a sump pit. It’s less invasive to install since it doesn’t require exterior digging, but it’s addressing water that has already arrived rather than keeping it out entirely.
An interior system is often paired with a sump pump to move the collected water out of the basement.
Signs an Existing Drain May Have Failed
- Water seeping in along the base of basement walls, especially after heavy rain
- A sump pump that runs far more often than it used to
- Visible efflorescence (a white mineral residue) on basement walls, which can indicate persistent moisture migration
- Standing water or unusually soggy ground directly next to the foundation
Drain systems can clog with sediment or roots over time, particularly older installations without a fabric sock around the pipe. A drain that’s failing doesn’t always need full replacement; sometimes it can be flushed or partially repaired.
Frequently Asked Questions
Is a French drain the same as a weeping tile?
They describe the same basic concept: a gravel-and-pipe drainage trench. “Weeping tile” is the term more commonly used in Canada, historically referring to old clay drain tiles laid with small gaps that let water “weep” in; “French drain” is the more common term across the rest of North America. Modern systems using perforated plastic pipe are functionally similar regardless of which name is used locally.
How long does a French drain last?
Properly installed systems can last several decades, but lifespan depends heavily on soil conditions, whether the pipe has a filter sock, and whether nearby tree roots are a factor. Older systems installed without modern filter fabric tend to clog with fine sediment sooner.
Do I need both an interior and exterior drain?
Not always. Many homes are adequately protected with just an exterior system, just an interior system, or good surface grading and gutters alone. Whether both are worthwhile depends on the severity of the water problem, the age of any existing drainage, and site-specific conditions best assessed in person.
Sources
- General drainage engineering literature on perimeter drain (French drain / weeping tile) design and function
- Canadian residential construction terminology distinguishing “weeping tile” from “French drain”