Moderate for very simple, small-scale systems with significant research and careful planning. Professional consultation is highly recommended for optimal design, sizing, and proper installation to ensure code compliance and long-term effectiveness, especially given local soil conditions and frost depth requirements.
The proper design and installation of a stormwater dry well system in DuPage County involves careful site assessment, soil percolation testing, accurate sizing based on impervious area and rainfall data, adherence to the 42-inch frost depth for all drainage components, and compliance with local plumbing and environmental regulations to ensure effective long-term drainage and prevent property damage or public health risks.
Project Guidelines & Rules
General Requirements & Permitting
3 Rules
Permit Application
Consult your local municipality's building department for specific permit requirements prior to commencing work. IL Plumbing Code (General applicability for drainage systems).
Site Plan Submission
A detailed site plan indicating the proposed dry well location, dimensions, contributing impervious areas, and setbacks must be submitted to the local building department. IRC R106.1
Compliance with Local Ordinances
All installations must comply with specific local stormwater management ordinances and zoning requirements of your local municipality.
Site Assessment & Design
3 Rules
Soil Percolation Testing
Essential for determining the soil's ability to absorb water. Tests must be performed by a qualified professional to ensure the dry well is suitable for the site and correctly sized. IL Plumbing Code (Implied requirement for effective drainage system design).
Minimum Setbacks
Maintain adequate separation from property lines, building foundations (minimum 20 feet from structural foundations), septic systems, and potable water wells (minimum 50 feet). Adhere to local zoning ordinances. IRC R403.1.2 (for foundations) principles apply to drainage.
Sizing & Capacity
The dry well's volume and infiltration area must be professionally calculated to manage stormwater runoff from the contributing impervious surfaces (e.g., roofs, patios) based on DuPage County's design storm events and soil characteristics. IRC (General requirement for adequate drainage systems).
Excavation & Placement
2 Rules
Excavation Safety
All excavation work must comply with OSHA trenching and excavation safety standards. IRC R403.1.1 (General excavation requirements).
Stable Base
The bottom of the excavation must be level, stable, and free of debris, with adequate soil bearing capacity to support the dry well structure. IRC R401.4.
Materials
3 Rules
Dry Well Structure
Approved materials include pre-cast concrete rings, proprietary plastic chambers, or gravel-filled pits. Structures must be designed for longevity and proper infiltration.
Aggregate Fill
Use clean, washed aggregate (e.g., AASHTO No. 57 or No. 2 stone) with a high void ratio, free from fines, typically 3/4 to 1-1/2 inch in diameter.
Geotextile Fabric
Non-woven, permeable geotextile fabric must line the excavation walls and base (if applicable) to prevent soil migration into the aggregate, ensuring long-term infiltration capacity. Overlap fabric seams by at least 12 inches.
Piping & Connections
4 Rules
Inlet Piping Material
Schedule 40 PVC, corrugated HDPE, or other approved rigid, smooth-wall drainage pipe must be used for connections to downspouts, area drains, or other stormwater sources. IL Plumbing Code Section 890.320 (Building Storm Drainage).
Inlet Pipe Sizing
Inlet pipes must be appropriately sized based on the contributing drainage area and anticipated flow, ensuring no restriction to stormwater flow. IL Plumbing Code Section 890.320.
Watertight Connections
All connections to the dry well must be secure and watertight to prevent exfiltration around the dry well structure. IL Plumbing Code Section 890.320.
Overflow Provision (Recommended)
For larger systems or areas prone to heavy rainfall, a high-level overflow pipe connected to a public storm sewer or other approved secondary drainage area is highly recommended to prevent surface flooding during extreme events. IRC R106.1 (General drainage principles).
Drainage & Frost Protection
3 Rules
Infiltration Capacity
The dry well design must ensure sufficient infiltrative surface area on the sides and bottom to effectively disperse collected stormwater into the surrounding soil.
Minimum Burial Depth for Pipes
All stormwater drainage pipes leading to or from the dry well must be buried at or below the DuPage County established frost depth of 42 inches (3 feet, 6 inches) to prevent freezing, pipe damage, and disruption of flow. IRC P2603.6.1 (Protection from freezing), IL Plumbing Code (General principles for buried drainage).
Dry Well Depth for Frost Stability
While not directly an IPC requirement for the structure itself, the effective infiltrative layers of the dry well should ideally extend below frost depth to ensure consistent performance year-round and minimize frost heave potential.
Electrical (If Applicable)
2 Rules
Sump Pump Discharge to Dry Well
If a sump pump or other electrically-driven system discharges into the dry well, its electrical installation must comply with the 2023 NEC, including proper circuit sizing, GFCI protection, and outdoor wiring methods. NEC Article 210 (Branch Circuits), NEC Article 220 (Feeders), NEC Article 406.9 (Receptacles in damp/wet locations).
Underground Wiring Protection
All underground electrical wiring and conduit must be rated for wet locations, approved for direct burial (if applicable), and installed at the minimum burial depths specified in NEC Table 300.5 to prevent damage. NEC 300.5 (Underground Installations).
Maintenance & Inspection
3 Rules
Maintenance Access
Provide an accessible clean-out or inspection port for periodic removal of accumulated sediment and debris to maintain the dry well's infiltration capacity. Manufacturer recommendations for proprietary systems.
Inlet Screening
Install leaf screens or debris filters at all inlet points (e.g., downspout connections) to prevent large organic matter from entering and clogging the dry well.
Routine Inspection
Regularly inspect the dry well for signs of clogging, standing water, or reduced performance, especially after heavy rainfall.