A residential dry well installation starts with a percolation test, requires both a local building permit and federal registration under the EPA’s Underground Injection Control program, and ends with a stone-and-fabric-lined pit holding a perforated chamber that captures roof runoff and lets it soak into the ground. Each step has rules attached, and skipping any of them tends to show up later as a fine, a failed system, or an argument with a neighbor whose yard is now wetter than yours.
Test Your Soil First
Everything else depends on how fast water moves through the ground where you plan to dig. A percolation test saturates a hole overnight, then measures how quickly the water level drops the next day, reported in minutes per inch. Clay-heavy soil that barely drains will not support a dry well at all. If your result points to clay, look at rain gardens or surface swales instead.
The perc rate feeds directly into the sizing math, along with the square footage of roof draining into the system and your area’s rainfall intensity. Most local codes require the well to handle at least a one-inch storm without overflowing. A certified soil scientist or engineer typically charges between $250 and $1,500 to run the test and document it, with the higher end covering difficult terrain or a full engineering report. The written result also strengthens your permit application.
While you’re on site, classify the soil as sandy, silty, loamy, or clay-based. Your permit paperwork will ask, and the classification affects both the well’s volume and the stone you use around it.
Permits You Actually Need
Federal Registration Under the UIC Program
The EPA classifies dry wells as Class V injection wells because they send non-hazardous fluids underground, into or above drinking water sources.1U.S. Environmental Protection Agency. Basic Information About Class V Injection Wells The Safe Drinking Water Act requires every state to run an Underground Injection Control program for exactly this reason.2Office of the Law Revision Counsel. 42 US Code 300h – Regulations for State Programs
In practice, you submit inventory information to your state’s UIC Program Director: the facility location, your contact information, what you’re injecting (stormwater, for a residential dry well), and the well’s depth and construction.3eCFR. 40 CFR Part 144 Subpart G – Requirements for Owners and Operators of Class V Injection Wells The registration itself is free. Your state environmental agency or the EPA regional office can confirm whether the state or EPA administers the program where you live.
A boundary worth knowing: federal rules prohibit operating any injection well in a way that lets contaminants reach underground drinking water.4eCFR. 40 CFR 144.12 – Prohibition of Movement of Fluid Into Underground Sources of Drinking Water That rules out dry wells on properties used for vehicle maintenance, chemical storage, or handling of hazardous materials, and on sites with known soil or groundwater contamination. Call your state environmental agency before buying materials if any of that fits your property.
Local Building or Stormwater Permit
Nearly every municipality requires a separate permit before you dig. Expect to submit technical drawings showing the proposed location, the system’s dimensions, the calculated flow rate, the contributing drainage area, your soil classification, and your percolation test results. Forms usually live on the local building department’s online portal. Residential permit fees generally run $50 to $300.
Setbacks are non-negotiable and vary by jurisdiction. Common minimums include at least ten feet from building foundations and five feet from property lines, though your local code may demand more. Drinking water wells are a separate and much larger concern: many states require 100 to 500 feet of horizontal separation between a dry well and any water supply well. Violate a setback and you can face fines or an order to remove the system.
Keep the paperwork. If a neighbor later blames your drainage project for a wet basement, a permitted, code-compliant installation on file is your best defense.
Call 811 Before You Dig
Federal law requires using your state’s one-call notification system to locate underground utilities before any excavation.5Office of the Law Revision Counsel. 49 USC 60114 – One-Call Notification Systems Dial 811 at least two to three business days before you plan to break ground; the exact lead time depends on your state. Utility crews come out and mark gas, water, electric, and telecom lines with paint or flags. Markings are typically good for 28 calendar days, so if your schedule slips, request a re-mark.
The call is free. Hitting a gas line is a safety emergency; cutting a fiber optic cable can mean a repair bill in the thousands. If you’re using a contractor, confirm in writing who holds the 811 ticket, because responsibility can shift depending on contract language.
Materials to Have on Hand
Open pits are an invitation to problems, so gather everything before excavation day.
- A pre-cast concrete or high-density polyethylene chamber with perforated sides. Larger properties or high-runoff areas may need multiple chambers.
- Washed crushed stone, sized one and a half to two and a half inches, enough for a six-inch base plus a full surround with at least twelve inches of clearance on every side of the chamber.
- Heavy-duty non-woven geotextile filter fabric to wrap the stone and keep surrounding soil from migrating in.
- Rigid four-inch PVC pipe to carry water from downspouts to the chamber, plus primer, solvent cement, and any elbows or couplings the layout calls for.
- An overflow mechanism, usually a pop-up emitter or overflow pipe, so storms that exceed capacity have somewhere to go other than back through your downspouts.
A backhoe handles the excavation quickly on most lots. Hand-digging works for smaller or less accessible jobs, but it turns a few hours of machine work into a weekend of shoveling. Have a level, a tape measure, and a way to compact backfill ready.
Installation, Step by Step
Dig the Pit
Make the pit large enough to hold the chamber with at least twelve inches of stone clearance on all sides. Depth comes from two numbers: the volume your soil test called for, and your local frost line. The chamber must sit below the frost line so freeze-thaw cycles don’t crack it or heave the inlet pipe loose. Frost depth runs from near zero in the deep South to over six feet in northern states, so pull the number from your local code rather than guessing.
Line the bottom and walls with a continuous sheet of geotextile fabric, leaving extra at the top to fold over later. Spread a six-inch base of washed crushed stone across the bottom for a level, draining foundation.
Set the Chamber and Connect the Pipe
Lower the chamber onto the stone base using straps or equipment appropriate to its weight. Connect the four-inch PVC inlet pipe to the pre-cut opening in the chamber wall, running it at a slope of at least one-quarter inch per foot from the source so gravity carries water through and flushes sediment along with it. Seal joints with primer and solvent cement, or use mechanical gaskets if the chamber is designed for them. A leaking joint here means digging the whole thing up later.
If you’re adding an overflow line, connect it now. Route it to a pop-up emitter at a low point in the yard, well away from your foundation and your neighbors’ property. The emitter opens under pressure when the well fills and closes when flow stops.
Backfill and Finish
Fill the space between the chamber and pit walls with crushed stone, working evenly around all sides to keep the unit centered. Bring the stone up to the top of the chamber, then fold the excess geotextile fabric over the stone to seal it from surface soil. That fabric barrier is what separates a system that lasts decades from one that silts up in a season. Fine soil infiltrating the stone reservoir is the single most common reason dry wells fail early.
Cover with topsoil, bring the area back to grade, compact lightly without over-packing, and stabilize the surface with sod or mulch. Before you call it done, run water through the inlet pipe. If it flows freely and the chamber drains, you’re finished. If it doesn’t, you want to know now, not during the next storm.
Excavation Safety
Dry well pits often reach five feet or deeper, which is the OSHA threshold for requiring a protective system against cave-ins. Even shallower excavations need protection if a competent person (OSHA’s term for someone trained to identify hazards and authorized to stop work) sees signs of unstable soil.6Occupational Safety and Health Administration. 29 CFR 1926.652 – Requirements for Protective Systems
For most residential projects, the practical answer is to slope the pit walls back from the bottom at an angle keyed to soil type: roughly 53 degrees for cohesive clay (Type A), 45 degrees for medium soils like silt and angular gravel (Type B), and about 34 degrees for loose sand, gravel, or soft clay (Type C).7Occupational Safety and Health Administration. 29 CFR 1926 Subpart P Appendix B – Sloping and Benching In loose Type C soil, the opening at grade can end up three times as wide as the bottom. If your lot can’t accommodate that, a trench box or shoring system is the alternative, and at that point hiring a contractor with the right equipment often costs less than renting trench safety gear for a one-time job.
Keeping the System Working
A dry well that gets regular attention can function for decades. Some municipalities have documented systems still working after more than 80 years. The maintenance is simple and easy to skip.
After any significant rain, check the downspout filters and sediment traps feeding the system. Leaves and roof grit build up fast in spring and fall and will clog the inlet pipe if ignored. At least once a year, open the chamber’s access cap and gauge the sediment inside. If it reaches roughly a quarter of the chamber’s volume, call for professional vacuuming. Let it go past that point and fine particles start sealing the soil pores around the well, which is damage that vacuuming cannot undo. From there, the only fix is full replacement.
Water pooling on the surface above or near the well after moderate rain is the clearest sign of failure. So is water backing up through downspouts, soggy soil that doesn’t dry between storms, or erosion around the inlet. These usually mean the surrounding soil has sealed because fine sediment got past the filter fabric, either from fabric deterioration or poor installation.
Check for a Stormwater Fee Credit
If your municipality charges a stormwater utility fee based on impervious surface, a properly installed dry well that handles your roof runoff may qualify for a credit. Some cities offer credits of up to 100 percent for homeowners who manage rooftop runoff through approved green infrastructure, which includes dry wells, rain gardens, and similar systems. Call the stormwater utility before you install so you know what documentation they’ll want in your application.