Connecticut Grease Trap and Interceptor Requirements

Grease traps and grease interceptors are mechanical plumbing devices required by code at food service establishments, commercial kitchens, and other facilities that discharge fats, oils, and grease (FOG) into municipal sewer systems. Connecticut enforces these requirements through a combination of state plumbing code standards, Department of Energy and Environmental Protection (DEEP) regulations, and local sewer authority ordinances. Non-compliance carries consequences ranging from sewer surcharges to permit revocation, making accurate specification and maintenance critical for facility operators and licensed plumbing contractors alike. The Connecticut Plumbing Authority provides this reference to describe how grease interceptor requirements are structured across the state.

Definition and scope

A grease trap — also called a grease interceptor in larger-capacity configurations — is a plumbing device designed to intercept and retain FOG and solids before wastewater enters a municipal sanitary sewer or private septic system. The distinction between the two terms is codified in the International Plumbing Code (IPC), which Connecticut adopts as the basis for its State Plumbing Code under the Connecticut State Building Code (Connecticut Department of Administrative Services, Office of State Building Inspector).

• Hydromechanical grease interceptors (HGI): Small, under-sink or floor-mounted units rated by flow capacity in gallons per minute (GPM). Typical installations serve individual fixtures such as pot sinks or pre-rinse stations. IPC Table 1003.3.4.1 governs sizing for these units.
• Gravity grease interceptors (GGI): Large, below-grade or external vault-type units measured in total liquid capacity (gallons). These serve entire facilities or multiple fixture groups and are required when total fixture drainage flow exceeds the capacity thresholds of hydromechanical units.

Scope of this page: This reference addresses Connecticut-specific requirements under state plumbing code and applicable environmental regulations. It does not cover federal pretreatment standards enforced by the EPA under 40 CFR Part 403, which apply separately to significant industrial users. Requirements for on-site septic system design — including grease interceptors serving facilities on private sewage disposal — fall under Connecticut DEEP Regulations for the Subsurface Sewage Disposal System (DEEP Subsurface Sewage Disposal) and are not fully addressed here. Municipal sewer authority rules vary by jurisdiction and may impose stricter standards than state minimums; those local ordinances are not covered on this page.

How it works

Grease interceptors function through differential density. FOG, which is less dense than water, rises to the surface within the interceptor chamber while cooled wastewater exits through a submerged outlet baffle. Solids settle to the bottom. The retained FOG and solids are then removed through periodic pumping and disposal at a licensed facility.

The operational cycle for a compliant installation involves 4 discrete phases:

1. Specification and sizing: A licensed Connecticut plumber calculates required interceptor capacity based on fixture drainage load, peak flow rate, and applicable IPC sizing tables. Gravity interceptors are typically sized at a minimum 1,000-gallon capacity for full-service restaurants under most local sewer authority guidelines, though specific minimums vary by authority.
2. Permit issuance: A plumbing permit is required prior to installation. For commercial projects, the permit is obtained through the local building department; projects involving connection to a municipal sewer may also require separate approval from the local sewer authority. Details on the permit workflow are described in Connecticut Plumbing Permit Process.
3. Installation and inspection: Installation must be performed by a Connecticut-licensed plumber. Inspections are conducted by the local building official and, where applicable, the sewer authority's pretreatment inspector. Rough-in dimensions, access risers, and inlet/outlet baffle specifications are verified at inspection.
4. Maintenance and documentation: Facilities are required to maintain cleaning and pumping logs. Hydromechanical units typically require cleaning every 1 to 3 days under heavy use; gravity interceptors are generally pumped when the combined FOG and solids layer reaches 25% of total liquid capacity, a threshold referenced in EPA guidance on FOG control programs (EPA Fats, Oils, and Grease (FOG) Control).

Common scenarios

Food service establishments: Full-service restaurants, cafeterias, and institutional kitchens are the primary regulated category. Any establishment with a commercial dishwasher, three-compartment sink, or cooking hood drainage is subject to interceptor requirements under Connecticut's adopted plumbing code.

Tenant build-outs in multi-tenant commercial buildings: When a food service tenant occupies a space in a building not previously permitted for food preparation, a grease interceptor must be added as part of the build-out plumbing scope. This triggers both a plumbing permit and, frequently, a sewer connection review. Applicable commercial installation standards are covered under Connecticut Commercial Plumbing Requirements.

Renovation and change of use: A change in occupancy classification from retail to food service — even without structural alteration — constitutes a regulated trigger for grease interceptor installation under the IPC and Connecticut Building Code. Connecticut Plumbing Renovation and Remodel Rules addresses the broader trigger framework for existing buildings.

Mobile food units and commissaries: Connecticut DEEP and local health departments regulate mobile food units through commissary agreements. The commissary kitchen, not the mobile unit itself, bears the grease interceptor compliance obligation.

Decision boundaries

The threshold questions that govern which type of device is required, and who has jurisdiction, follow a structured logic:

Contractor qualification: Only Connecticut-licensed plumbers are authorized to install, modify, or repair grease interceptors under state law. Connecticut Plumbing License Requirements defines the licensure classifications applicable to commercial plumbing work. The regulatory context for Connecticut plumbing provides the broader statutory framework within which these requirements operate.

Inspection authority: The local building official holds primary inspection authority for plumbing installations. Sewer authorities exercise independent inspection authority over pretreatment infrastructure under their municipal ordinances. Neither authority substitutes for the other.

Out-of-scope situations: Private residential kitchens are not subject to grease interceptor requirements under the IPC or Connecticut plumbing code. Single-family dwellings, including those used for small licensed catering operations, fall outside the commercial FOG control mandate unless the local sewer authority has adopted a specific residential FOG ordinance — an uncommon but legally permissible local action.

References

• Connecticut State Building Code — Department of Administrative Services, Office of State Building Inspector
• Connecticut Department of Energy and Environmental Protection (DEEP) — Subsurface Sewage Disposal System Permits
• International Plumbing Code (IPC) — International Code Council
• U.S. EPA — Fats, Oils, and Grease (FOG) Control Programs
• 40 CFR Part 403 — General Pretreatment Regulations for Existing and New Sources of Pollution (eCFR)
• Connecticut Department of Public Health — Plumbing and Piping Licensing