Moderate. While physically achievable for capable homeowners, expert knowledge of hydrology, local soil conditions, and precise code compliance (especially for sizing and setbacks) is crucial. Professional consultation or installation is recommended to ensure efficacy and compliance.
Requires careful planning for site selection, sizing, excavation depth (accounting for DuPage County's 42-inch frost line), and adherence to local stormwater management principles. Material selection and proper installation are critical for long-term performance.
Project Guidelines & Rules
General Requirements
2 Rules
Purpose: Dry wells shall be constructed for the sole purpose of managing stormwater runoff from impervious surfaces (e.g., roofs, patios).
General Principle of Stormwater Management
Prohibited Connections: Under no circumstances shall dry wells be connected to sanitary sewers, septic systems, or used for gray water disposal.
Illinois Plumbing Code 890.130
Permitting & Inspections
3 Rules
Permit Application: Obtain all necessary permits from your local building department prior to commencing any work.
2024 IRC R105.1
Required Inspections: Schedule and pass all mandated inspections (e.g., pre-backfill, final) as required by your local building department.
2024 IRC R109.1
Documentation: Provide detailed site plans, drainage calculations, and material specifications with the permit application.
Local building department requirement
Site Selection & Soil Considerations
3 Rules
Location: Maintain minimum required setbacks from foundations, property lines, potable water wells, and septic systems as determined by your local municipality or health department.
2024 IRC R401.3 (Implications for Drainage), Local Amendments
Soil Suitability: Evaluate soil conditions (e.g., percolation rates) to ensure adequate infiltration. Soil testing is highly recommended for optimal performance.
Best Practice, often required by local stormwater management ordinances
Utility Locates: Contact J.U.L.I.E. at 811 before any excavation to locate underground utilities.
Illinois Underground Utility Facilities Damage Prevention Act (220 ILCS 50)
Excavation & Frost Depth
3 Rules
Excavation Depth: The bottom of the dry well system must extend below the 42-inch frost depth characteristic of DuPage County to prevent frost heave and ensure continuous infiltration capacity.
DuPage County Regional Standard (consistent with 2024 IRC R403.1.4.1 concept)
Inlet Pipe Frost Protection: All inlet piping connecting to the dry well must be protected from freezing, typically by burial below the 42-inch frost depth or by using approved insulation methods.
2024 IRC R403.1.4.1 (concept for foundations, extended to plumbing)
Excavation Safety: All excavation work must adhere to OSHA safety standards, including shoring, sloping, or shielding as required.
OSHA 29 CFR 1926 Subpart P
Sizing & Capacity
2 Rules
Sizing Calculations: The dry well's volume and surface area must be calculated based on the impervious area it serves, local rainfall intensity data, and validated soil percolation rates.
Illinois Plumbing Code 890.1360.e, DuPage County Stormwater Management Ordinance (as applicable)
Stormwater Event Design: The dry well shall be designed to adequately manage runoff from at least a 2-year, 24-hour storm event as a minimum, or as specified by local stormwater management regulations.
Best Engineering Practice, local DuPage County Stormwater Management requirements
Construction & Materials
5 Rules
Dry Well Structure: Approved dry well structures include pre-cast concrete rings, perforated plastic chambers, or stone-filled pits constructed with durable materials designed for subsurface conditions.
General Construction Practice, Manufacturer Specifications
Geotextile Fabric: A non-woven geotextile fabric shall be used to line the excavation, covering the bottom and all sides, to prevent soil migration into the aggregate while allowing water infiltration.
Best Engineering Practice for Drainage Structures
Aggregate Material: Use clean, washed gravel (e.g., 3/4" to 1.5" diameter) with minimal fines to fill the dry well void, ensuring maximum storage and infiltration capacity.
Best Engineering Practice
Inlet Piping: Connect incoming stormwater with heavy-duty PVC (e.g., Schedule 40 or SDR 35) or corrugated HDPE pipe suitable for underground burial.
Illinois Plumbing Code 890.1360.f, Manufacturer Specifications
Cover: Install a secure, load-bearing cover (e.g., reinforced concrete slab, heavy-duty grate) if the dry well is located in areas subject to vehicle or pedestrian traffic. Otherwise, a suitable layer of topsoil and landscaping is acceptable.
General Safety and Structural Integrity
Drainage Connections & Slope
3 Rules
Direct Connection: All downspouts or other stormwater runoff sources directed to the dry well must be connected via solid, watertight piping.
Illinois Plumbing Code 890.1360.f
Minimum Slope: Connecting pipes shall be installed with a minimum downward slope of 1/8 inch per foot (1%) to ensure proper gravity drainage.
Illinois Plumbing Code 890.1360.c
Overflow Provision: If an overflow is utilized, it must connect to an approved storm sewer or designated surface discharge area, complying with all local stormwater regulations.
Illinois Plumbing Code 890.1360.d, Local Stormwater Ordinances
Electrical Considerations
2 Rules
Non-Applicability: A standard gravity-fed dry well typically does not involve electrical components.
2023 NEC (No direct application)
Pump Integration: If a pump system is used to discharge into a dry well (e.g., from a sump pit), all electrical wiring, equipment, and installations must comply strictly with the 2023 National Electrical Code.
2023 NEC Articles 210.8 (GFCI), 250 (Grounding), 300 (Wiring Methods), 430 (Motors)