Yard Drainage and French Drains: Fixing Standing Water

Standing water in a yard usually comes from one of three sources — surface runoff pooling in a low spot, a high water table saturating soil from below, or roof/downspout water dumping faster than soil can absorb — and each needs a different fix. A French drain (a gravel-filled trench with a perforated pipe) solves subsurface saturation and intercepting groundwater well, but it does little for pure surface ponding, which usually needs regrading or a surface (catch basin) drain instead.

How do you diagnose which type of drainage problem you have?

1. Watch the yard during and right after a heavy rain — water sheeting across the surface toward a low point points to a grading problem; water seeping up through the lawn slowly over the following day points to a high water table or poor soil percolation.
2. Dig a test hole about 12 inches deep and fill it with water; if it doesn't drain within 12-24 hours, the soil itself has poor percolation and any drain needs to carry water to daylight or a dry well rather than relying on the surrounding soil to absorb it.
3. Check whether downspouts discharge near the wet area — a disconnected or short downspout extension is one of the most common and cheapest-to-fix causes of a chronically soggy spot near the foundation.
4. Note whether the wet area is downhill from a neighboring property or impervious surface like a driveway, which may be redirecting water onto your lot.

How is a French drain sized and built?

What is a dry well and when do you need one?

A dry well is a gravel-filled pit (or a perforated plastic chamber) that collects water and lets it infiltrate slowly into surrounding soil, used when there's no lower point on the property to daylight a drain to. Sizing depends on soil percolation rate and the catchment area feeding it — a typical residential dry well handling one downspout runs 3-4 feet in diameter by 3-4 feet deep, filled with washed stone, but poor-draining clay soil may need it 2-3 times larger to handle the same volume.

When does regrading solve the problem better than a drain?

If the problem is purely surface water pooling in a shallow low spot with no groundwater involvement, adding 1-2 inches of soil sloped at a minimum 2% grade (about 1/4 inch per foot) away from the area is often cheaper and more permanent than a subsurface drain, since it eliminates the low spot rather than draining it. Regrading against a house foundation should always slope away for at least the first 6-10 feet, per most building codes, to prevent water intrusion at the foundation.

What does a French drain project typically cost?

• DIY materials for a 50-foot French drain: roughly $300-600 for pipe, gravel, and fabric, plus rental of a trencher (~$100-150/day) if not hand-digging.
• Professional installation of the same run: $1,500-4,000 depending on depth, soil conditions, and access.
• A dry well addition: $1,000-3,000 depending on size and excavation difficulty.
• Simple regrading of a problem area under 500 square feet: $500-1,500 for material and equipment, often less than a comparable drain installation.

How does a catch basin or channel drain differ from a French drain?

A catch basin (a grated box set into the grade at a low point) collects surface water directly at the point it pools and pipes it away below ground, which makes it the right tool for pure surface ponding rather than subsurface saturation. A channel or trench drain, a long narrow grated trough, serves a similar purpose along a linear path, such as at the base of a driveway apron or across a walkway where sheet-flow crosses it. Both differ from a French drain in that they intercept water at the surface rather than pulling it from saturated soil below grade, and both need to tie into the same kind of gravity-fed outlet — daylight, storm system, or dry well — or they simply relocate the ponding problem a few feet.

What plants or landscaping choices help with chronically wet areas?

A rain garden — a shallow, planted depression that collects and slowly infiltrates runoff — complements drainage work in spots that stay damp even after grading and drains are improved, typically planted with species tolerant of both standing water and dry spells, such as switchgrass or red-twig dogwood. Turf performs poorly where soil stays saturated more than a day or two, so converting that spot to a planted bed often solves the aesthetic problem even when drainage can't be fully corrected.