Brentwood, CA · East Contra Costa
Dry Well Installation in Brentwood, CA
A dry well is an underground pit or chamber that holds water from downspouts or a French drain and lets it soak into the ground slowly. It's a useful outlet when there's nowhere else to send the water. In clay soil, though, it has to be sized and placed honestly, or it simply fills up.
Cited cost ranges · No obligation
When a dry well makes sense
There's no place to daylight water
A flat lot with no lower ground and no practical route to the street can still have an outlet: a dry well.
Downspouts dump at the foundation
Running downspouts underground to a dry well a safe distance from the house keeps roof water away from the slab.
A French drain needs an end point
A dry well at the low end of a French drain gives collected water somewhere to go.
The soil drains reasonably well
Dry wells work best in soil that absorbs water. A percolation test tells you whether yours does before you pay for one.
How a dry well works
Water arrives through a solid pipe from downspouts, a catch basin, or a French drain. It fills a gravel pit or a perforated plastic or concrete chamber surrounded by gravel, and seeps out through the sides and bottom into the surrounding soil. A dry well doesn't make water disappear; it stores a storm's worth temporarily and releases it as fast as the soil allows. Many systems include an overflow so that, once the well is full, extra water exits at the surface somewhere harmless instead of backing up.
The clay-soil caveat
The USDA describes the Brentwood soil series, mapped in Contra Costa County, as clay loam over heavy clay loam with moderately slow permeability. Slow-draining soil means a dry well fills fast and empties slowly. That doesn't rule one out, but it means sizing should follow a percolation test, and an overflow matters. Be wary of a quote that promises a dry well will handle any amount of water.
Types of dry wells
| Type | What it is | Trade-offs |
|---|---|---|
| Gravel pit | An excavated hole filled with washed gravel, wrapped in fabric | Cheapest; holds less water per cubic foot than an open chamber |
| Prefabricated plastic chamber | A perforated plastic tank set in gravel | More storage in less space; common for residential downspouts |
| Concrete tank or ring | Precast concrete with openings, set in gravel | Highest capacity and cost; for larger volumes |
What it usually costs
Angi's 2026 yard drainage data puts a dry well installation at about $1,000–$4,000, with the unit itself $300–$1,000. HomeGuide (February 2026) lists the dry well materials alone at $50–$250 for a gravel pit, $200–$700 for a prefabricated plastic chamber, and $500–$3,000 or more for a concrete tank, and a percolation test at $600–$2,000.
Published ranges, not a quote; Bay Area jobs often cost more than national averages. Full breakdown: French drain cost in Brentwood.
Questions to ask before installing a dry well
- Will you test how fast the soil drains (a percolation test) before sizing the well?
- How far from the foundation, property line, and any septic system will it sit?
- What size chamber, and how many square feet of roof or yard will drain into it?
- Is there an overflow, and where does it go?
- Will a catch basin or filter keep debris out, and how is the well maintained?
Placement and distance requirements can vary, so ask the contractor what applies to your property and check with your city if you're unsure. If a dry well isn't a good fit, a French drain to daylight or a curb outlet, or downspout lines routed away from the house, may solve the same problem.
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
Do dry wells work in clay soil?
They can, but they drain slowly. In clay, a dry well needs to be sized from a percolation test, often larger than in sandy soil, and should have an overflow. Sometimes another outlet works better.
How much does a dry well cost?
Angi's 2026 data puts dry well installation at about $1,000–$4,000. HomeGuide (2026) lists materials from $50–$250 for a gravel pit up to $500–$3,000+ for a concrete tank. See the cost guide for related drainage costs.
How far should a dry well be from the house?
Far enough that the water it releases doesn't end up back at the foundation. The right distance depends on the soil, the slope, and local requirements, so ask the contractor and confirm with your city if needed.
Can downspouts drain into a dry well?
Yes, this is one of the most common uses. Downspouts connect to solid underground pipe that runs to the dry well, ideally through a debris filter or catch basin so roof grit doesn't fill the well.
Related drainage fixes
Downspouts & catch basins
Underground downspout lines, catch basins and channel drains for roof and patio water.
French drain installation
Underground pipe and gravel that collects soggy-yard water and carries it to a real outlet.
Standing water & soggy yards
Work out what's causing the water, then match it to the right fix.
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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