What Is a Dry Well and Why Do Florida Properties Need Them?
A dry well is an underground structure designed to collect stormwater runoff and slowly disperse it into the surrounding soil. In Florida, where 50 to 65 inches of rain falls annually and the rainy season dumps 60% of that between May and October, managing stormwater is not optional. It is a requirement for protecting your property, your foundation, and the environment.
Unlike surface drainage systems that redirect water elsewhere, dry wells handle stormwater right where it falls. They collect runoff from roofs, driveways, and patios, then allow it to percolate into the ground at a controlled rate. For Florida homeowners dealing with standing water, soggy yards, or local drainage regulations, dry wells offer a proven underground solution that keeps your landscape intact.
At StructureSmart Engineering, our Licensed Professional Engineers have designed dry well systems across South Florida for over 20 years. Here is what you need to know before installing one on your property.
How Dry Wells Work
A dry well is essentially an underground chamber, typically a perforated concrete, plastic, or gravel-filled pit that receives stormwater and releases it gradually into the surrounding soil. The basic mechanics are straightforward:
- Collection: Stormwater enters the dry well through inlet pipes connected to downspouts, catch basins, or surface drains
- Storage: The chamber temporarily holds the water during heavy rain events, preventing surface flooding
- Infiltration: Water seeps out through perforations or gaps in the chamber walls and disperses into the native soil
- Overflow protection: A properly designed system includes an overflow outlet to handle storms that exceed capacity
The key to dry well performance in Florida is soil permeability. Much of South Florida sits on sandy soil over limestone substrate, which generally provides good infiltration rates. However, areas with clay content, compacted fill, or high water tables require careful engineering to ensure the system works as intended.
Types of Dry Wells
There are three main types of dry wells used in Florida residential projects:
- Precast concrete dry wells: Heavy-duty perforated concrete cylinders, typically 3 to 4 feet in diameter. These are the most durable option and perform well in Florida's soil conditions. They resist flotation better than plastic alternatives when the water table is high.
- Plastic chamber systems: Modular plastic units that snap together to create underground storage. Brands like StormTech and Cultec are common in Florida installations. They are lighter, easier to install, and offer more storage volume per cubic foot than gravel pits.
- Gravel-filled pits: The simplest approach is a pit filled with clean, washed gravel (typically 1.5-inch stone). While cost-effective, gravel pits store less water per cubic foot because the gravel itself takes up about 60% of the space. The effective storage is only the void space between stones.
Sizing Requirements for Florida Conditions
Undersized dry wells are the number one reason these systems fail. In Florida, sizing must account for our intense rainfall rates, not national averages. A summer thunderstorm in Miami-Dade or Broward County can drop 2 to 4 inches of rain in a single hour.
Proper sizing depends on several factors:
- Contributing drainage area: The total impervious surface (roof, driveway, patio) directing water to the dry well. A 2,000-square-foot roof generates roughly 1,250 gallons of runoff per inch of rainfall.
- Design storm event: Most Florida jurisdictions require systems to handle the 25-year, 24-hour storm event, which ranges from 8 to 10 inches depending on your county. SFWMD (South Florida Water Management District) may require retention of the first inch of runoff on-site.
- Soil infiltration rate: Sandy soils in Florida typically infiltrate at 4 to 8 inches per hour, while areas with clay or muck may be as low as 0.5 inches per hour. A soil percolation test is essential before design.
- Water table depth: In South Florida, the water table can sit just 2 to 6 feet below the surface. The bottom of your dry well must be at least 2 feet above the seasonal high water table. This single factor often determines whether a dry well is feasible on your property.
Our engineers use hydrologic modeling software to calculate the exact volume needed for your specific site conditions, contributing area, and local regulatory requirements. A typical residential dry well in South Florida ranges from 50 to 300 gallons of effective storage capacity, though larger properties may need significantly more.
Installation Process
Dry well installation in Florida is more involved than digging a hole and dropping in a chamber. Proper installation follows a specific sequence to ensure long-term performance.
Step 1: Site Assessment and Soil Testing
Before any digging begins, we conduct a thorough site assessment including a soil percolation test to measure infiltration rates. In many South Florida locations, we also check the seasonal high water table elevation. If the water table is too high, a dry well may not be the right solution, and we will recommend alternatives like a French drain system or surface grading improvements.
Step 2: Excavation
The pit is excavated to the required depth and diameter, with at least 12 inches of clearance around the chamber for backfill material. In Florida's sandy soils, excavation is usually straightforward, but dewatering may be needed if the water table is encountered during digging.
Step 3: Base Preparation
A 6 to 12-inch layer of clean, washed gravel is placed at the bottom of the excavation. This creates a stable base and additional infiltration area. Filter fabric is wrapped around the gravel bed to prevent soil migration while allowing water to pass through.
Step 4: Chamber Placement
The dry well chamber is set on the gravel base and leveled. Inlet pipes are connected, and any overflow piping is installed. For plastic chamber systems, multiple units may be connected in series to achieve the required storage volume.
Step 5: Backfill and Connection
The space around the chamber is backfilled with clean gravel, wrapped in filter fabric to prevent sediment intrusion. Inlet pipes from downspouts, drainage pipes, or catch basins are connected and tested for proper flow.
Step 6: Final Grading
The surface is restored with topsoil and sod. A properly installed dry well is completely hidden underground with no visible components except access risers for maintenance inspection.
Florida Regulations and Permit Requirements
Dry well installations in Florida may require permits depending on your jurisdiction, property size, and the scope of the project. Here is what you need to know:
- SFWMD permits: Projects that affect surface water management in the South Florida Water Management District jurisdiction may require an Environmental Resource Permit (ERP). This is especially true for properties in flood zones or near wetlands.
- County requirements: Palm Beach, Broward, and Miami-Dade counties each have their own stormwater management regulations. Some require engineer-stamped drainage plans for any new impervious surface or changes to existing drainage patterns.
- HOA approvals: Many Florida communities have homeowner association requirements that govern drainage modifications. Check with your HOA before beginning any work.
- Setback requirements: Dry wells must be placed a minimum distance from property lines, foundations, septic systems, and wells. Typical setbacks include 10 feet from foundations and 50 to 100 feet from drinking water wells.
Our permit services team handles all regulatory filings and has maintained a 100% permit approval rate across 1,000+ projects. We know what each jurisdiction requires and design accordingly from the start.
Maintenance and Longevity
Dry wells are low-maintenance, but they are not maintenance-free. Florida's sandy soil and organic debris mean sediment can accumulate over time and reduce infiltration capacity.
- Annual inspection: Check the dry well through the access riser to ensure water is draining within 24 to 48 hours after a rain event. If water is standing longer, the system may need cleaning.
- Sediment removal: Every 3 to 5 years, have the dry well pumped and flushed to remove accumulated sediment. Florida's frequent storms carry significant debris.
- Inlet maintenance: Keep inlet grates, downspout filters, and catch basins clear of leaves and debris. Prevention is always cheaper than rehabilitation.
- Landscaping considerations: Keep tree roots away from the dry well. Root intrusion is a common cause of system failure, particularly with species like live oaks and ficus that are common in South Florida.
A well-designed and properly maintained dry well system should last 25 to 50 years. The key is getting the engineering right from the start and performing basic maintenance.
When to Call a Professional
Dry wells seem simple in concept, but getting the engineering wrong leads to expensive failures. You should consult a professional engineer when:
- Your property has a high water table (common throughout South Florida)
- You are adding impervious surfaces that change your property's drainage pattern
- Your municipality or HOA requires engineer-stamped drainage plans
- You have standing water problems that need a comprehensive solution
- Your property is in a flood zone or near environmentally sensitive areas
At StructureSmart Engineering, our Licensed Professional Engineers have designed dry well systems across Palm Beach, Broward, and Miami-Dade counties since 2004. We provide engineer-stamped designs that meet all local and SFWMD requirements, backed by our 100% permit approval rate. Schedule a free consultation or call us at (347) 998-1464 to discuss your project.
If cost is a concern, our drainage cost guide breaks down typical project pricing so you know what to expect before committing.
Frequently Asked Questions
How much does a dry well system cost in Florida?
A residential dry well installation in Florida typically costs between $1,500 and $5,000 depending on the size, type of chamber, soil conditions, and whether permits are required. Engineered designs with permit services add to the total but are often required by local jurisdictions. Our residential drainage design service starts at $2,500 for a complete, permit-ready plan.
Will a dry well work with Florida's high water table?
It depends on your specific location. The bottom of a dry well must be at least 2 feet above the seasonal high water table. In parts of South Florida where the water table sits at 2 to 3 feet below grade, traditional dry wells may not be feasible. Our engineers perform water table assessments as part of every design to determine if a dry well is appropriate for your property.
Do I need a permit for a dry well in Florida?
Permit requirements vary by county and municipality. In many South Florida jurisdictions, any modification to existing drainage patterns requires at minimum a site plan review. Larger systems or those near waterways or wetlands may require a full Environmental Resource Permit from SFWMD. Our team handles all permitting and knows the specific requirements for each jurisdiction.
How long does a dry well take to drain after rain?
A properly sized and functioning dry well should drain completely within 24 to 72 hours after a typical rain event. If water is standing longer than 72 hours, the system may be undersized, clogged with sediment, or the water table may be too high. This is why professional engineering and soil testing are critical before installation.
Can I install a dry well myself?
While small dry wells for a single downspout can be DIY projects, we strongly recommend professional engineering for any system serving more than a minimal drainage area. An improperly sized or placed dry well can make drainage problems worse, damage foundations, or violate local regulations. The cost of professional design is a fraction of the cost of fixing a failed installation.