Awaiting expert review. This page covers safety or regulatory rules that change over time. It is kept out of search results until a qualified reviewer has checked it; the sources below are dated so you can verify each point.
Quick answer
A dry well is an underground pit or shaft, filled with stone or fitted with a perforated chamber, that takes in water from a roof or drain and lets it soak slowly into the soil around it.
It stores a limited amount of water during a storm and releases it into the ground. Under EPA rules, many dry wells count as Class V injection wells, so local and state rules, soil, and groundwater depth decide whether one is allowed.
Quick facts
The key facts about Dry Well, with sources:
- What it is
- A vertical underground infiltration system fed by buried pipes from impervious surfaces 1
- EPA class
- Stormwater drainage wells, including dry wells, can be Class V injection wells 2
- EPA depth test
- A shaft or hole deeper than it is wide can qualify; wider than deep generally does not 2
- Permit model
- “Authorized by rule”: no individual permit if it does not endanger drinking water and basic inventory is filed 2
- Oregon groundwater clearance
- Roof runoff: 5 feet to the seasonal high water table; other runoff: 10 feet 1
- Typical depth, Oregon State
- 2 to 20 feet, and up to 30 feet is possible 1
Key takeaways
- A dry well lets water soak into the ground from below the surface. It is a last-resort tool, not a first fix.
- EPA says dry wells deeper than they are wide can be Class V injection wells. They are authorized by rule, but they must not endanger drinking water.
- Site limits matter: groundwater depth, bedrock, slope, and distance from foundations, property lines and drinking wells.
- Only clean roof and similar runoff belongs in one. EPA lists petroleum, metals, fertilizers and pesticides among stormwater contaminants of concern.
- Call 811 before digging, and never send overflow onto a neighbor’s land without an easement. Check local and state rules first.
A dry well in plain English
Think of a buried bucket with holes, packed in stone. Water from a downspout runs in through a pipe, fills the stone, and then seeps out into the surrounding soil. Nothing is pumped. The soil does the work.
Oregon State Extension defines drywells as “vertical, underground infiltration systems that receive runoff from impervious surfaces via buried pipes.”
They reduce runoff rate, volume and temperature by letting water slowly seep into the surrounding soils, and they temporarily store a limited volume of runoff during storms.
The fact sheet calls them a last resort, used when tools like rain gardens or porous pavement are impractical 1.
The word is also used loosely. Utah State Extension uses “vertical drains (dry wells)” for something smaller: a hole 4 to 6 inches in diameter and 3 to 5 feet deep dug in the bottom of a planting hole and filled with coarse gravel, to give water an exit 5.
That is a garden fix, not a stormwater well. This page covers the stormwater kind, which carries legal rules.
Dry well, drywell, seepage pit and planting-hole drain: which is which
| Name | What it is | Source note |
|---|---|---|
| Stormwater dry well | A vertical pit or chamber that receives piped runoff and infiltrates it | Oregon State Extension 1. EPA: also called bored wells and infiltration galleries 2 |
| Class V stormwater drainage well | A dry well or similar system that meets EPA’s well definition | EPA: used for subsurface infiltration to manage runoff 2 |
| Planting-hole vertical drain | A narrow gravel-filled hole under a planting pit | Utah State: 4 to 6 inches wide, 3 to 5 feet deep 5 |
| Shallow infiltration trench or bed | Wider than it is deep | EPA says systems larger at their widest surface point than they are deep generally are not Class V wells 2 |
Deeper than wide is the legal hinge
EPA quotes 40 CFR 144.3: a well is “a bored, drilled, or driven shaft whose depth is greater than the largest surface dimension.” A shallow trench wider than it is deep generally falls outside that definition, a deep pit does not 2. Which one you have changes the rules that apply.
How a dry well moves water, step by step
The chain is short, but each link has a limit.
- Runoff is collected. A downspout or drain sends clean water into a buried pipe.
- Pretreatment catches debris. Oregon State says water must be treated before it enters the drywell, and for roofs recommends a silt basin plus gutter screens 1.
- Water enters the chamber. It fills the stone or the perforated unit.
- Water seeps into soil. The soil’s infiltration rate decides how fast.
- Overflow has a path. Oregon State describes an overflow pipe to a splash block or a second facility 1.
- Inlet pipe and coverBrings in roof or drain water; access for inspection
- Silt basin or screenCatches debris before water enters 1
- Storage chamber or stoneHolds water briefly during a storm 1
- Sump or solid baseOregon State recommends a 3-foot solid sump to ease sediment removal 1
- Surrounding soilTakes the water by infiltration; must be at least 5 feet above seasonal high groundwater for roof runoff in Oregon 1
A schematic only. Depth, size and materials come from a design for your site and approval where required. Source: [1]
Example: what Oregon’s rules say about two kinds of runoff
Oregon State Extension’s fact sheet quotes the Oregon Department of Environmental Quality (ODEQ) and the City of Portland 1. The rules below are Oregon’s, shown to illustrate how runoff type changes the requirements. Your state may differ.
| Question | Roof runoff only | Runoff from driveways, parking or loading areas |
|---|---|---|
| Clearance from drywell bottom to seasonal high groundwater | 5 feet 1 | 10 feet 1 |
| Registration with ODEQ | Generally not needed for an individual residential roof drywell, unless the city requests review for high groundwater 1 | Must be registered and approved 1 |
| Pretreatment | Silt basin “highly recommended,” plus gutter screens 1 | Proprietary treatment with a filtering medium 1 |
| Reason for the difference | The fact sheet does not state one | EPA lists petroleum and other contaminants as concerns in stormwater generally 2 |
The point is not Oregon’s numbers. It is that the same pit faces stricter rules when the water touches pavement. A designer or local office should say which case you are in before any digging.
Where dry wells show up: drainage bids, site plans and permits
You meet a dry well as an outlet in a drainage plan, as a line item in a landscaping or drainage bid, or on a site plan for a new roof, addition or driveway. It is often proposed when a lot has no storm sewer or when a city wants runoff kept on site.
Ask any bidder to state three things: what water goes in (roof only, or pavement too), how deep the water table and bedrock are, and which office approved it.
The drainage and grading service page shows how this work is scoped. For a quick check of whether a wet yard needs a drain at all, use the drainage diagnostic.
A dry well can also be one choice of outlet for a French drain, which needs somewhere for its water to go. In that case the dry well’s own rules apply.
What a dry well can do
Where it helps
Where it falls short
- Needs soil that takes water, deep groundwater and enough distance from buildings 1.
- Must not carry polluted water into groundwater. EPA lists petroleum, metals, nutrients, fertilizers and pesticides among stormwater contaminants 2.
- Once it clogs it must be replaced, says Oregon State 1.
- Is a regulated well in many cases 2.
Limits: groundwater, bedrock, slope and clogging
A dry well needs room under it. Oregon State, quoting ODEQ, requires 5 feet between the bottom of a drywell and the top of the seasonal high groundwater table for roof runoff and 10 feet for other runoff.
It also lists bedrock higher than 10 feet below the bottom of the facility as a place where infiltration should not occur 1.
A dry well also cannot work if the soil will not take water, so test soil first. See soil drainage and infiltration.
Slope matters too. The same fact sheet excludes slopes “exceeding 10 percent or in landslide areas,” while elsewhere it says slopes of 20 percent or greater require geotechnical evidence. The two numbers do not match, so check local rules before assuming either 1.
Clogging ends the life of the well. Oregon State says properly maintained drywells can last decades, but once a facility clogs it must be replaced 1. Pretreatment and a sump slow that down.
Finally, a dry well does not replace other fixes. A wet yard from a high water table or poor grading may need a different tool, covered in the landscape grading term.
- If Groundwater is closer than your rule’s clearance (5 or 10 feet in Oregon)
- Then No. Pick another outlet 1
- If Bedrock sits within 10 feet below the bottom (Oregon rule)
- Then No 1
- If Water would include driveway or parking runoff
- Then Expect registration and treatment; ask your state UIC office 12
- If Soil does not take water in a test
- Then No. Use a different design
- If Roof water only, deep groundwater, soil that infiltrates
- Then Possible, with local approval and a design
What drives the cost of a dry well, and how long it lasts
We do not publish prices.
These drivers move a bid: the depth and diameter of the pit, the number of units, the soil and any test, the cost of excavation and hauling spoil, the stone or manufactured chamber, the pretreatment (silt basin and screens), the pipe run from the roof, the overflow path, and any design or approval fee.
A site where groundwater or bedrock is shallow may rule it out, which saves money before any digging.
For general drainage budgets, see the cost guide. For volume of stone, the gravel calculator does the arithmetic.
On life, the only source we loaded that speaks to it is Oregon State: “Properly maintained drywells can last decades,” and once a facility clogs, it must be replaced 1. We found no warranty standard. Ask the installer what is covered.
Who installs it, and the order of steps
A dry well is not a typical homeowner project. A drainage contractor or civil engineer designs and builds it, and a state or local office may need to approve or register it. Permits and inspection vary by place.
- Ask the local office first. Contact your city or county stormwater office and your state UIC program about whether the structure is allowed.
- Test the soil and find groundwater and bedrock depth.
- Check setbacks from foundations, property lines, septic systems and drinking wells.
- Call 811 before any digging. USA North 811 says the service is free and to wait for each utility’s response 6.
- Design with pretreatment and an overflow path.
- Register or file inventory information if required. EPA lists typical inventory items such as location, contact, ownership, type of well and status 2.
- Build, test and keep records.
Never put anything but clean runoff in, and keep overflow on your own land
EPA says stormwater may carry petroleum and other organic compounds, sediment, nutrients, metals, salts, microorganisms, fertilizers and pesticides that can harm drinking water sources 2.
Do not pour oil, paint, chemicals or wastewater into a dry well. Oregon State says excess runoff should never go to neighboring private property without a utility easement 1. Call 811 before digging 6.
Keeping a dry well working
- Keep gutters and screens clean. Oregon State recommends gutter screens to filter debris 1.
- Clean the silt basin or sump. A 3-foot solid sump makes sediment removal easier 1.
- Look at the overflow outlet after big storms.
- Keep lawn chemicals and spills away from drains. EPA names fertilizers and pesticides among contaminants 2. See lawn chemical safety.
- Keep the cover accessible and do not park on it unless it is rated for that.
Warning signs a dry well is failing
- Water backs up in downspouts or stands near the cover after rain.
- The overflow runs often. The well may be full or clogged.
- Wet ground or settling near the pit. It may be leaking or collapsing.
- Dampness at a nearby foundation. Too little setback, or saturated soil, can push water toward a building. Stop sending water to the well and call a professional.
- Odors or sheen mean something other than clean roof water got in.
Persistent signs call for a licensed drainage contractor or engineer. Oregon State says once a drywell clogs it must be replaced, so ask for an inspection before spending on cleaning 1.
Rules and standards: EPA Class V wells, state programs and local codes
Federal law, the Safe Drinking Water Act. EPA says Class V wells are injection wells not included in other well classes, that over 20 subtypes fall into the group, and that they are regulated by the Underground Injection Control program under the Safe Drinking Water Act 34.
Owners and operators are responsible for protecting underlying groundwater from contamination 4.
Authorized by rule. EPA says stormwater drainage wells can operate without an individual permit if the injection does not endanger an underground source of drinking water and the owner submits basic inventory information to the permitting authority. It adds that inventory requirements vary by state 2.
The definition. EPA quotes 40 CFR 144.3, “a bored, drilled, or driven shaft whose depth is greater than the largest surface dimension,” and says a shaft, dug hole or trench deeper than it is wide can be a Class V well, as can subsurface piping that discharges to the subsurface 2.
State and local rules. Oregon State Extension says ODEQ treats drywells as Class V wells, and that state rules prohibit injection where better treatment or protection is an option, such as when a municipal sewer is available within 300 feet of the site 1.
Portland adds setbacks of 5 feet from property lines and 10 feet from foundations 1. Those are Oregon and Portland rules, not national ones.
Standard vs law. Extension guidance, such as the depth range of 2 to 20 feet, is voluntary advice. EPA’s UIC program, state rules and city codes are binding where they apply.
- 650,000+Class V wells EPA estimated in the US in a 1999 study of 23 well typesEPA, Basic Information About Class V Injection Wells
- Over 20Well subtypes in the Class V groupEPA, Class V Wells page
- 5 ft / 10 ftOregon clearance to seasonal high groundwater, roof runoff vs other runoffOSU Extension EM 9200
- 300 ftOregon distance to a municipal sewer that can bar injectionOSU Extension EM 9200
Dry well compared with other places to send water
| Option | What it does | How it differs from a dry well |
|---|---|---|
| Dry well | Infiltrates piped runoff into soil from a vertical pit 1 | The baseline here |
| French drain | Carries soil water along a trench to an outlet 7 | Moves water along a line; see the French drain term |
| Catch basin | Collects surface water at a grate | Collects and passes on; may have no infiltration |
| Rain garden or swale | Infiltrates in a shallow planted area | Shallow and open. EPA says systems wider than deep generally are not Class V wells 2 |
| Storm sewer or street | Sends water to a public system | Needs permission from the owner of that system |
Dry well myths
- Myth A dry well is just a hole in the yard, with no rules.
- Reality EPA says many are Class V injection wells, regulated under the Safe Drinking Water Act 32.
- Myth Any water can go in.
- Reality EPA lists petroleum, metals, fertilizers and pesticides among contaminants of concern 2.
- Myth It works anywhere.
- Reality Oregon rules bar infiltration where groundwater or bedrock is too close 1.
- Myth It lasts forever.
- Reality Oregon State: properly maintained drywells can last decades, but once clogged, replace 1.
Your state’s UIC program and local stormwater rules decide
The regional variables are your state’s underground injection control rules, depth to groundwater, soil and local stormwater code. EPA says inventory requirements vary by state 2.
Oregon’s numbers, such as 5 or 10 feet to groundwater and a 300-foot sewer rule, are Oregon’s alone 1.
Look up soil conditions and flooding patterns for your area in the soil drainage research, and ask your city or county stormwater office what applies.
When a dry well makes sense, and the next step
A dry well may make sense for clean roof runoff on a lot with no storm sewer, soil that takes water, deep groundwater and bedrock, and enough room from buildings and property lines. It makes little sense with shallow groundwater, tight soil, or runoff from driveways without treatment and approval.
The next step is a call to your local stormwater office and state UIC program, then a soil and groundwater check by a professional. If you hire a company, ask who holds the design responsibility and see how to choose a landscaping company.
Questions about Dry Well
What is a dry well?
A dry well is an underground pit or shaft that takes in runoff from a roof or drain and lets it soak into the soil. Oregon State Extension calls drywells vertical, underground infiltration systems that receive runoff from impervious surfaces through buried pipes. They are a last resort when tools like rain gardens are impractical.
Do dry wells need a permit?
It depends on the place. EPA says stormwater drainage wells are authorized by rule, meaning no individual permit if they do not endanger drinking water and basic inventory is filed. Oregon State says residential roof drywells generally need no ODEQ registration, but those serving driveways or parking must register. Check your state.
Is a dry well an injection well?
Often, yes. EPA says Class V stormwater drainage wells include dry wells, bored wells and infiltration galleries, and that a shaft or hole deeper than it is wide can qualify. Systems wider than deep generally do not. Class V wells are regulated under the Safe Drinking Water Act.
How deep should a dry well be?
It depends on soil, groundwater and design. Oregon State Extension says typical depths run from 2 to 20 feet, and up to 30 feet is possible. In Oregon, the bottom must stay 5 feet above seasonal high groundwater for roof runoff and 10 feet for other runoff. Your designer sets depth.
How far should a dry well be from a house?
Oregon State Extension says Portland requires 5 feet from property lines and 10 feet from foundations, with 8 feet for small plastic units, and that drywells should be 20 feet from cesspools and 500 feet from drinking wells. Those are Oregon figures. Local building rules and an engineer decide for your lot.
What can go into a dry well?
Clean runoff, mainly from roofs, with pretreatment. EPA lists petroleum, sediment, nutrients, metals, salts, microorganisms, fertilizers and pesticides as contaminants of concern in stormwater. Do not pour oil, chemicals or wastewater into a dry well. Pretreatment, such as a silt basin and gutter screens, is advised.
How long does a dry well last?
Oregon State Extension says properly maintained drywells can last decades, and that once a facility clogs it must be replaced. A silt basin, gutter screens and a solid sump slow clogging. We found no standard warranty, so ask the installer what it covers.
What is the difference between a dry well and a French drain?
A dry well infiltrates water into the soil from a vertical pit. A French drain carries soil water along a trench to an outlet. A French drain still needs an outlet, and a dry well is one possible choice. Each has its own rules, covered on its term page.
Can I build a dry well myself?
Most are not homeowner projects. They involve digging, soil and groundwater checks, setbacks, pretreatment, possible registration and utility locates. Call 811 before any digging. A contractor or engineer familiar with your state’s rules is the safer choice.
Where else can roof water go instead?
Several places, depending on rules and site: a splash block onto a graded lawn, a rain garden, a swale, a French drain to a lower outlet, or a storm system where allowed. Never a neighbor’s land without an easement, and never a sanitary sewer. Ask your stormwater office.
Sources
- Oregon State University Extension, Drywells: Low-impact development fact sheet (EM 9200; Godwin, Cahill and Tilt; May 2018, reviewed 2022), retrieved .
- US EPA, Stormwater Drainage Wells (updated Jan. 20, 2026), retrieved .
- US EPA, Basic Information About Class V Injection Wells (updated Dec. 29, 2025), retrieved .
- US EPA, Class V Wells for Injection of Non-Hazardous Fluids into or Above Underground Sources of Drinking Water (updated Feb. 26, 2026), retrieved .
- Utah State University Extension, Solutions to Soil Problems III. Drainage (June 2010), retrieved .
- USA North 811, DIYers (call 811 before you dig), retrieved .
- Colorado State University Extension, Soil Drainage (GardenNotes 219, reviewed Sept. 2022), retrieved .
Expert review
Written by the HyreYard Research Desk. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: EPA Class V definitions and the authorized-by-rule model were read on the EPA pages cited; Oregon figures were read in Oregon State Extension’s fact sheet and are labeled as Oregon and Portland rules.
Held under G-REV: a licensed engineer or state UIC authority has not reviewed this page. No design, size or rate is given.
Suggest a correction. We fix errors and say what changed.