Prepared by GreaseTrapLocator · Fact review: August 8, 2026
Three device categories
Hydromechanical grease interceptor (HGI)
A listed device evaluated by a rated flow and grease-retention performance. Correct flow control, venting, installation, access, and the accepted model matter.
Gravity grease interceptor (GGI)
A larger tank that provides separation and storage under a locally approved design. Capacity, compartments, covers, access, installation, and local sizing method matter.
Automatic grease-removal device
A listed unit that separates grease and mechanically moves collected grease into a container. The current manual, service routine, and local acceptance matter.
Other marketed products
A drawer, dosing product, or biological treatment is not automatically a separate code category or an approved replacement. Ask the authority about the exact product and claim.
Separation needs controlled flow
FOG separation depends on giving grease an opportunity to separate instead of pushing it through the device. Turbulence is not a benefit to advertise. The accepted flow-control arrangement, internal components, installation, and maintenance condition all affect performance.
How to compare products
| Question | HGI | GGI | Automatic device |
|---|---|---|---|
| Primary rating to verify | Certified flow and grease retention | Approved tank capacity/design | Listing, flow performance and removal system |
| Approval evidence | Listing, manual and local acceptance | Approved plans, local method and tank documents | Listing, manual and local acceptance |
| Maintenance question | Who may inspect and fully clean it? | Who may pump, transport and document the contents? | Who services the separation and removal components? |
Do not select a device from a national price, payback, cleaning interval, or kitchen-size shortcut. Compare the approved function, model documentation, access, maintenance responsibility, and full project quote.
Official sources used
New York City Department of Environmental Protection
Hydromechanical interceptors, gravity grease interceptors, and automatic grease-removal devices are distinct device categories with different sizing provisions.
15 RCNY §19-11, Best Management Practices for Non-Residential Dischargers of Fat, Oil, and Grease · link updated October 15, 2026
U.S. Environmental Protection Agency
FOG can solidify, reduce sewer capacity, and block flow; 40 CFR 403.5(b)(3) prohibits solid or viscous pollutants in amounts that obstruct flow and result in interference; local programs establish controls.
Controlling Fats, Oils, and Grease Discharges from Food Service Establishments · reviewed August 8, 2026
Seattle Public Utilities
Seattle uses a 25 percent trigger when manufacturer specifications are unavailable, prohibits emulsifying agents/enzymes/bio-additives, supplies local self-cleaning guidance, and directs a business with a backup into the premises to close and contact public health.
Fats, Oils, & Grease: Commercial Kitchens · reviewed August 8, 2026
Austin Water
Austin warns businesses not to buy before plan approval and publishes its own fixture-unit sizing criteria.
Grease Trap Sizing & Design Criteria · reviewed August 8, 2026
Frequently asked questions
Are there exactly five types of grease traps?
No. Product marketing uses many labels. For plan review, start with the recognized device category and the exact listed model accepted by the local authority.
Is an HGI gallon capacity the same as its flow rating?
No. A flow rating and a liquid volume describe different characteristics.
Are enzymes or biological additives a grease-interceptor type?
No. They are treatment products, and some local programs prohibit their use. Confirm the local rule before using any additive.
Which device is cheapest?
This guide does not provide a national price answer. Compare approved equipment and itemized current project quotes with the maintenance responsibilities included.
Author: Grease Trap Locator Editorial Team
The Grease Trap Locator editorial team covers FOG compliance, grease trap maintenance, and commercial kitchen regulations across the US and Canada. Our guides are written for restaurant owners, facility managers, and food service operators who need practical, accurate information without the fluff.
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