Brentwood, CA · East Contra Costa
French Drain Installation in Brentwood, CA
A French drain is a gravel-filled trench with a perforated pipe that collects water underground and carries it somewhere it can leave your yard. Installed in the right place, with a real outlet, it ends the soggy lawn and the water against the house. Installed in the wrong place, it is an expensive gravel strip.
Cited cost ranges · No obligation
When a French drain is the right fix
The lawn stays wet for days after rain
Water is moving through the soil, not just sitting on top. A subsurface drain intercepts it and gives it somewhere to go.
Water reaches the foundation from uphill
On a sloped lot or below a neighbor's yard, an interceptor (curtain) drain across the slope catches water before it gets to the house.
A side yard turns to mud
Narrow side yards between a house and a fence collect runoff from two roofs. A shallow French drain along the fence line is a common fix.
Planters and beds hold water
Raised beds and planters against stucco walls can trap water. A drain at the base keeps the wall and the plants dry.
How a French drain works
Water takes the easiest path. A trench filled with washed gravel is an easier path than clay soil, so groundwater and surface water seep into it. A perforated pipe at the bottom of the trench, laid with a steady downhill slope, carries that water to an outlet: a spot where it can daylight on a slope, reach the street through a curb outlet, or soak into a dry well. Filter fabric wrapped around the gravel keeps fine soil from clogging the system over time.
- 1Surface and topsoil. Sod, rock, or mulch over the trench. Water soaks down to the gravel faster than through the clay around it.
- 2Filter fabric. Wraps the gravel on all sides and keeps clay fines out. Skipping it is the usual reason drains clog.
- 3Washed gravel. Clean, uniform stone gives water an easy path to the pipe.
- 4Perforated pipe on a slope. Holes facing down, laid with a steady fall so water flows the whole way.
- 5The outlet. Daylight, a curb outlet where allowed, or a dry well. Without one, a drain just fills up.
Illustration. Not to scale; depth, width, and pipe size vary by yard.
Every part matters, but the outlet matters most. A French drain with nowhere to send water just fills up. When you get quotes, the first question is where the water goes. Depth, slope, and fabric choices are covered step by step in how a French drain is installed.
Common French drain layouts
| Layout | Where it goes | What it solves |
|---|---|---|
| Interceptor (curtain) drain | Across a slope, uphill of the house or the wet area | Water arriving from uphill or from a neighbor's yard |
| Lawn or field drain | Through the low or soggy part of the yard | A lawn that stays saturated after rain |
| Side-yard drain | Along the fence or the house in a narrow side yard | Mud and pooling between two roofs |
| Foundation-edge drain | A few feet out from the foundation, below the slab edge | Water collecting against the house (often paired with grading and downspout lines) |
Not every wet yard needs a French drain
If the problem is water from the roof, downspout lines are cheaper. If the yard slopes toward the house, regrading may be the real fix. If water pools on a patio, a catch basin or channel drain fits better. Start with what's causing the standing water.
What it usually costs
HomeGuide (February 2026) puts an exterior yard French drain at about $10–$35 per linear foot, or $1,000–$3,500 for 100 feet. Angi's 2026 data averages $20–$50 per foot for French drains. A Bay Area contractor's 2026 guide (Cardona Construction) quotes $35–$90 per foot locally, with clay soil slowing excavation, so East County jobs often land above national averages.
Published ranges, not a quote; Bay Area jobs often cost more than national averages. Full breakdown: French drain cost in Brentwood.
French drains in East County soil
Much of East Contra Costa sits on clay and clay-loam soils. The USDA's description of the Brentwood soil series, mapped in Contra Costa County, lists clay loam over heavy clay loam with moderately slow permeability. In plain terms: water soaks in slowly, so a yard can stay wet long after a storm, and trenching takes more effort than in sandy soil. Two things follow for a French drain here. The outlet needs to move water off the property rather than counting on the soil to absorb it, and fabric around the gravel matters more, because clay fines are what clog a drain.
What a French drain installation involves
- Assessment. The contractor walks the yard after (or during) rain, finds where water comes from and where it can go, and checks the fall available to the outlet.
- Utility marking. Underground lines are marked before digging. California's 811 service is free, and its operator says notice is required at least two working days before excavation.
- Trenching. Typically a narrow trench, deeper and wider for foundation-edge or interceptor drains. Sod and plants are set aside where possible.
- Fabric, gravel, pipe. Fabric lines the trench, washed gravel goes in, the perforated pipe is set on grade, then more gravel and the fabric is folded over.
- Outlet and cleanouts. The pipe connects to the outlet. Good systems include a cleanout so the line can be flushed later.
- Restoration. Backfill, then sod, rock, or mulch. Ask whether lawn and landscape repair is included or extra.
What to ask for in a French drain quote
- A simple drawing showing the drain route, linear feet, and the outlet
- Trench depth and width, pipe type and diameter, and whether the pipe is perforated or solid in each section
- Filter fabric: yes or no, and where
- Cleanouts and how the system can be flushed
- What restoration is included: sod, irrigation repair, concrete patching
- Warranty terms, payment schedule, and the contractor's license number to verify at cslb.ca.gov
The full checklist, with red flags, is on choosing a yard drainage contractor.
Check any contractor, including one you find here
- Ask for the contractor's CSLB license number and look it up at cslb.ca.gov. The CSLB site also explains when a California contractor license is required.
- Get the quote in writing: the length and depth of each drain, the pipe and gravel, filter fabric, where the outlet is, and how the yard will be restored.
- Be wary of large deposits or cash-only terms. Ask who marks utilities through 811 and who handles any permit the city requires.
- Ask the contractor to show you the route and the fall from the farthest inlet to the outlet, and what warranty covers the work.
This site is an independent referral service, not a contractor. Your request goes to an independent local drainage contractor, who gives the quote and does the work. How this works
Common questions
How much does it cost to have someone put in a French drain?
National guides put exterior yard French drains at roughly $10–$50 per linear foot (HomeGuide 2026, Angi 2026), and a Bay Area contractor's 2026 guide quotes $35–$90 per foot locally. A 100-foot yard drain is often a few thousand dollars. See the French drain cost guide.
How deep does a French drain need to be?
It depends on the job. Shallow lawn and side-yard drains are often 18 to 24 inches deep; foundation-edge and interceptor drains go deeper. What matters as much as depth is a steady slope to a working outlet. Details are in how a French drain is installed.
What are the downsides of a French drain?
Cost, disruption to the yard, and clogging over time if fabric is skipped or the outlet is poor. A French drain also does nothing for roof water or a yard that slopes toward the house. The honest list is in French drain pros, cons and alternatives.
Where does the water from a French drain go?
To an outlet: daylight on a lower part of the property, a curb outlet to the street where the city allows it, or a dry well. Rules on connecting to the street or storm drain vary by city, so ask the contractor and check with your city before the work starts.
Who installs French drains near Brentwood?
Drainage specialists, landscape contractors, and some general and plumbing contractors. You can request a quote from an independent local drainage contractor through this site, and compare any quote using the contractor checklist.
Related drainage fixes
Standing water & soggy yards
Work out what's causing the water, then match it to the right fix.
Dry wells
An underground chamber that lets drain water soak in. Useful as an outlet, limited by clay soil.
French drain repair
Signs a drain has clogged or failed, what flushing and repair involve, and when to replace it.
Hiring a drainage contractor
A quote checklist, the questions to ask, red flags, and how to check a license.
Talk to a local drainage pro
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