Grease Control Program



The presence of fats, oils and grease in wastewater can result in major operational problems in sewer lines and pump stations owned by the Narragansett Bay Commission (NBC), cities and towns, and at the wastewater treatment facilities. Grease discharged down the drain may also plug up plumbing in homes and businesses. Grease causes problems in sewers by solidifying on the inside walls of sewer pipes restricting the flow of sewage, similar to the way that cholesterol restricts the flow of blood through arteries and veins. Sewer line backups and complete blockages have resulted from grease build up, causing raw sewage to back up onto public streets or into the basements of homes and businesses. Further, grease has fouled equipment and controls at treatment facilities, and high concentrations of grease and oils in wastewater can inhibit the biological wastewater treatment processes reducing the level of treatment we can provide.


 Grease Blocking Sewer Pipe Clean Sewer Pipe
Grease Blocking Sewer Pipe Clean Sewer Pipe


Program Goal

The NBC Grease Removal Program goal is to control the discharge of fats, oils and grease from restaurants and food preparation facilities into the sewer system. Grease discharges are predominantly generated from washing and cleaning operations and not from fryolators or deep frying units as most people might think. The pot washing sinks and dishwasher pre-rinse stations in restaurants and food preparation facilities are the major sources of grease discharges to the sewer system.  Click here for more information on NBC's Fats, Oils, and Grease - Environmental Results Program (FOG-ERP). 



Wastewater Discharge Permit Required

Certificate to DischargeThe NBC controls the discharge of fats, oils and grease through the issuance of Wastewater Discharge Permits. All commercial and industrial facilities which may conduct food preparation operations are required to obtain a wastewater discharge permit from the NBC Pretreatment Section. Facilities required to obtain a discharge permit to control grease discharges may include restaurants, hotels, hospitals, colleges and universities, schools, nursing homes and other facilities that may have a cafeteria or commercial kitchen.


Typical permit requirements may include the installation of a Grease Removal or Recovery Unit (GRU) that meets NBC criteria, properly maintaining the GRU, and keeping records documenting GRU maintenance activities.

Click here to obtain a wastewater discharge permit application.

Grease Removal or Recovery Unit (GRU)

Automatic electrical mechanical GRUA GRU is a device designed to collect and remove grease from wastewater. Most GRUs separate grease from water by gravity.  Since grease weighs less than water, the grease floats and can be skimmed from the surface of the wastewater.

Section 1003.3.1 of the International Plumbing Code requires a GRU be installed to receive the drainage from fixtures and equipment with grease-laden waste located in food preparation areas. There are two types of GRU’s that are acceptable for installation in the NBC districts. One type of GRU is the automatic electrical/mechanical GRU. The other acceptable type is the large in-ground passive type of GRU. Prior to purchasing or installing a GRU, approval must be granted from NBC Pretreatment office. Pretreatment staff will provide guidance throughout the review and approval process to ensure the GRU selected meets NBC criteria, avoiding the need for costly retrofits.

Click here for a list of equipment manufacturers of grease removal systems.

In Ground Passive GRU

GRU Approval and Installation

Prior to purchasing or installing a GRU, approval must be granted from NBC Pretreatment staff. NBC staff provides guidance necessary to ensure that the GRU selected meets NBC criteria. Contacting the Pretreatment section at 401-461-8848, ext. 490 in advance may prevent a company from incurring expensive GRU retrofit costs should initial installation not satisfy NBC criteria. To receive approval, technical information on the proposed GRU must be submitted to the NBC along with plans of the kitchen facility. The plans must show all wastewater generating equipment and piping to the GRU. A sample port directly downstream of the GRU must be shown on the plans. There must be a minimum eight inch clearance for the installation of sampling bottles.

Example of Basic Kitchen Diagram