Start With Gravity
Every component described here moves water downhill. None of them pump, none of them work uphill, and none of them function without somewhere lower to discharge to.
That means the first question in any drainage design is not which component to use. It is where the water can legitimately go. If there is no outlet at lower elevation than the collection point, the design is constrained before it starts. Our drainage improvements page covers how that assessment works.
French Drains
What it is. A trench containing perforated pipe bedded in washed gravel, typically wrapped in a geotextile fabric filter, running from a collection area to a discharge point.
How it works. Water in the soil migrates into the gravel, which offers less resistance than the surrounding ground. From the gravel it enters the perforated pipe and flows by gravity to the outlet. The fabric keeps fine soil out of the gravel, which is what determines whether the drain still functions in ten years.
Where it fits. Where subsurface water moves through the soil toward a structure, or where surface water needs intercepting along a slope before it reaches the house.
What it needs. Genuine fall along its length and a viable outlet. A level trench full of gravel is a reservoir, not a drain, and it sits against your foundation.
Details that matter. Fabric wrapping and how it is lapped, gravel size and washing, pipe perforation orientation, and how the trench is capped at the surface.
Catch Basins
What it is. A box set into the ground with a grate at the surface, connected to solid outlet piping.
How it works. Surface water flows to the low point, enters through the grate, collects in the basin, and exits through the pipe by gravity. Most basins include a sump below the outlet so sediment settles rather than entering the pipe.
Where it fits. A defined point where water visibly collects: a dip in a lawn, the bottom of a slope, a patio corner that holds water after rain.
What it needs. To sit at the actual low point, which is not always where it looks like it should be, and an outlet with fall.
Maintenance. Basins collect leaves, silt, and debris along with water, and they need periodic clearing. This is the component most likely to fail through neglect rather than through installation.
Swales
What it is. A shallow, deliberately shaped channel formed by regrading the ground surface.
How it works. Water follows the channel to where you want it rather than sheeting across the ground or collecting.
Where it fits. Wherever there is space and fall. Directing runoff around a structure, carrying water from a high point to a discharge area, or intercepting flow from a neighbouring property.
Why it is often the best option. There is nothing buried to silt up, nothing to fail mechanically, and nothing to maintain beyond keeping the channel clear. Where a swale will do the job, it usually outlasts everything else.
Limitation. It needs surface space and it changes how the yard looks and mows.
Solid Outlet Piping and Gutter Extensions
What it is. Non-perforated pipe carrying water from a collection point to a discharge location without letting it back into the soil along the way.
Where it fits. Downspout connections carrying roof water underground and clear of the structure, and as the outlet run from basins and French drains.
Why it matters more than people think. A roof delivers an enormous volume in a Texas storm. Getting that volume away from the perimeter is frequently the highest-value drainage work on a property, and it is comparatively inexpensive.
Channel and Trench Drains
Linear grated drains set flush into paving, used where a driveway, patio, or walkway needs to shed water across its width rather than at a point. Common at garage entries and across driveway approaches.
Sump Basin and Pump
Used only where gravity fall is genuinely unavailable: flat sites, or where the collection point sits below every available outlet. A pump adds mechanical failure points, power dependency, and maintenance. Where gravity will work, gravity is the better system.
Choosing Between Them
| Situation | Component |
|---|---|
| Water moving through soil toward the house | French drain |
| Water collecting at a defined low point | Catch basin |
| Water needing directing across open ground | Swale |
| Roof water arriving at the perimeter | Gutter extension or solid pipe |
| Water crossing a paved surface | Channel drain |
| No available gravity outlet | Sump basin and pump |
Most properties needing drainage work use more than one, because water behaves differently in different parts of a yard.
On outlets and neighbours
Where water discharges matters legally as well as practically. Discharging onto a neighbouring property or into a drainage easement without regard for how it functions creates a problem that is not solved by having fixed yours. Outlet options are established during the assessment, before anything is designed.
Maintenance
- Clear catch basins of leaves and sediment, particularly after storms and through autumn.
- Check outlets for vegetation growth and debris.
- Watch for water surfacing where it should not, which usually indicates a blockage upstream.
- Avoid disturbing fabric-wrapped sections during landscaping work.
Our guide on when drainage work is recommended with foundation repair covers the sequencing question where both are in play.