Drainage
Surface Drainage Decision Guide
Choosing among grading, swales, catch basins, and french drains on clay sites — with the slopes and pipe sizes that make each one work.
Drainage work in North Texas has one governing fact: clay barely percolates. Water here is managed on the surface and moved by gravity — solutions that rely on soaking into the ground fail slowly and expensively. Use this decision path before quoting.
Decision path
- Can regrading alone move the water? Always the first and cheapest answer. Code standard is 5 percent fall for the first 10 feet away from a foundation (about 6 inches); established beds and turf need a minimum of 2 percent to shed reliably.
- Is there a path for surface flow? Shape a turf swale — a broad, mowable dish 6 to 12 inches deep, falling at 1 to 2 percent — to carry roof and lot water to the street or an approved discharge.
- Is water concentrating where it cannot flow away (courtyards, bed low points, downspout discharge)? Catch basins piped to daylight or the curb are the workhorse: surface water enters a grate and gravity does the rest.
- Is the problem subsurface — saturated soil against a wall, seeping slopes, soggy zones that never dry? Only then is a french drain the tool.
- No gravity outlet at all? A sump with a pump is the honest answer; say so early. Dry wells in clay are a disappointment subscription.
| Symptom | System | Key numbers |
|---|---|---|
| Water against foundation | Regrade + downspout pipes | 5 percent for first 10 ft; extensions to daylight |
| Sheet flow across lot | Turf swale | 1 to 2 percent fall; 6 to 12 in deep, 4 to 6 ft wide |
| Ponding low spots | Catch basins + solid pipe | 12-in basins typical; 4-in SDR-35 or SCH 40 at 1 percent minimum |
| Roof water volume | Dedicated downspout lines | One 4-in line handles 2 to 3 downspouts; no corrugated pipe |
| Saturated subsoil / seeps | French drain | Perforated pipe, washed gravel, fabric-wrapped, to daylight |
| Paved areas / door thresholds | Channel drain | Tie to solid pipe; grate rated for the traffic |
Rules for pipe runs
- Slope solid pipe at 1 percent minimum (1/8 inch per foot); 2 percent where you can get it. Shoot grades with a laser — eyeballing fall over 80 feet is how backfalls happen.
- Use smooth-wall PVC (SCH 40 or SDR-35). Corrugated black pipe crushes under mowers and traffic, silts because of its ribs, and cannot be jetted clean — the price difference is not worth the callbacks.
- Discharge legally: to the street gutter through a curb core, to daylight on falling grade, or per city rules — never onto a neighbor. Cap discharge with a pop-up emitter only when there is enough fall to lift it (about a foot of drop across the run); otherwise daylight the pipe.
- Put a cleanout or basin every 50 to 75 feet and at direction changes on long runs.
- In new landscapes, run drainage pipe before planting and sleeve under all hardscape at rough-in.
The french drain caveat
In clay, an unwrapped french drain silts shut in a few seasons. Wrap the gravel envelope in non-woven geotextile, use washed stone (not fines), and give the pipe a gravity outlet. And do not sell a french drain for a surface-water problem — surface water wants a grate, not gravel.
Diagnose in the rain
Walk the property during or immediately after a storm, or run hoses for thirty minutes. Photograph where water stands, where it enters, where it exits, and time how long the ponding lasts. Standing water that clears within a day is a grading conversation; water that lingers for days in a bed is a soil and subsurface conversation. The rain walk turns a vague complaint into a scoped, priced fix — and clients sign scoped fixes.
We stock basins, grates, SDR-35 and fittings, washed gravel, and fabric as contractor bundles — bring the site sketch and footages and we will help you kit the whole run in one pull.
Have a question about material for this job? Call the yard at (817) 431-9490 or browse live inventory.