Not recommended for DIY due to the technical complexity, specialized equipment requirements, strict code compliance, and potential environmental impact.
Installation involves precise sizing, significant excavation (especially for in-ground units considering DuPage County's 42-inch frost depth), adherence to multiple specialized plumbing and electrical codes, and careful coordination with various inspection stages.
Project Guidelines & Rules
I. Permitting & Pre-Installation
3 Rules
Obtain necessary plumbing and building permits from your local municipality prior to commencement of work.
Illinois Plumbing Code 890.130, local building department requirements
Submit detailed site plans, plumbing drawings, and grease trap sizing calculations for review.
Illinois Plumbing Code 890.Appendix A, local building department requirements
Conduct a site survey to identify existing utilities and ensure proper placement of the grease trap.
JULIE One Call (811), local building department requirements
II. Grease Trap Sizing & Selection
4 Rules
Select an approved grease interceptor type (hydro-mechanical or gravity) suitable for the application.
Illinois Plumbing Code 890.730(a)
Size the grease trap based on flow rate, retention time, and anticipated FOG (Fats, Oils, and Grease) loading from fixtures discharging into it.
Illinois Plumbing Code 890.730(b)
Hydro-mechanical grease interceptors (HGI) must be certified to ASME A112.14.3 or PDI G101 and properly sized.
Illinois Plumbing Code 890.730(b)(1)
Gravity grease interceptors (GGI) must comply with design and construction standards, including a minimum volume of 750 gallons.
Illinois Plumbing Code 890.730(b)(2)
III. Excavation & Foundation (for In-Ground Units)
3 Rules
Excavation for the grease trap and associated piping must extend below the established DuPage County frost depth.
42 inches minimum below grade (DuPage County Regional Standard), Illinois Plumbing Code 890.310
Provide a stable, level, and adequately compacted foundation or support pad for the grease trap unit.
Illinois Plumbing Code 890.310(a), 2024 IRC R401, R403 (for general foundation principles)
Ensure excavation safety measures, including proper shoring for trenches exceeding 5 feet in depth, are implemented.
OSHA 29 CFR 1926 Subpart P, general construction safety standards
IV. Plumbing Connections & Venting
5 Rules
Connect all fixtures that may discharge FOG into a separate drainage system leading to the grease trap.
Illinois Plumbing Code 890.730(c)
Install piping with adequate slope (minimum 1/4 inch per foot) to ensure proper flow and prevent clogs.
Illinois Plumbing Code 890.730(c), 890.410
Provide proper venting for the grease trap system to prevent siphoning and ensure atmospheric pressure.
Illinois Plumbing Code 890.900 through 890.960
Install accessible cleanouts at strategic locations for maintenance and inspection.
Illinois Plumbing Code 890.810
For gravity grease interceptors, install an approved sampling port downstream of the interceptor.
Illinois Plumbing Code 890.730(b)(2)(D)
V. Electrical Requirements (If Applicable)
4 Rules
Provide a dedicated branch circuit with appropriate overcurrent protection for any automatic or sensor-equipped grease traps.
2023 NEC 210.20, 210.21
Ensure all electrical receptacles serving a grease trap are protected by a Ground-Fault Circuit-Interrupter (GFCI).
2023 NEC 210.8
Utilize wiring methods and equipment suitable for damp or wet locations as required by the installation environment.
2023 NEC 300.5, 314.15
Properly ground and bond all electrical equipment and components related to the grease trap.
2023 NEC 250
VI. Installation, Access & Backfilling
4 Rules
Install the grease trap level and secure all connections to ensure a watertight system.
Illinois Plumbing Code 890.310, manufacturer's specifications
Provide readily accessible covers for inspection, pumping, and maintenance of the grease trap.
Illinois Plumbing Code 890.730(d)
Access covers in vehicular traffic areas must be rated for the anticipated load.
2024 IRC R301 (general structural load principles), local engineering standards
Backfill around the grease trap with approved material, compacted in layers, taking care not to damage the unit or piping.
General construction standards, manufacturer's specifications
VII. Testing & Inspections
4 Rules
Perform a watertight test on the grease trap and all associated plumbing prior to backfilling.
Illinois Plumbing Code 890.610
Schedule and pass a rough-in plumbing inspection before concealing any piping or the grease trap.
Illinois Plumbing Code 890.620(a), local building department requirements
Schedule and pass a final plumbing inspection upon completion of all work.
Illinois Plumbing Code 890.620(b), local building department requirements
If applicable, schedule and pass a final electrical inspection for any powered components.
2023 NEC 80.29, local building department requirements
VIII. Post-Installation & Maintenance
3 Rules
Establish a regular maintenance schedule for cleaning and pumping the grease trap to ensure optimal performance and prevent FOG discharge into the sewer system.
Illinois Plumbing Code 890.730(e)
Ensure proper disposal of all removed grease and solids by a licensed waste hauler.
Local waste disposal regulations, environmental protection guidelines
Maintain detailed records of all cleaning and maintenance activities.
Illinois Plumbing Code 890.730(e)
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