Issue: 6/03

A grease pit, as far as a restaurant owner is concerned, can be nothing but a money pit. Unless there is a recycling facility, the units provide no direct financial benefit to the restaurant, are expensive to install and require continual maintenance. Unfortunately, like a lot of things in life, grease collection and disposal is a necessary evil. The expense of not having grease interceptors is dramatic. I cannot calculate the billions of dollars saved in environmental damage and maintenance expenses of the public sewer systems thanks to grease interceptors. To balance the competing values of profitability for the restaurant owner and environmental protection, a grease collection system must be designed to meet performance criteria for the application and balance the economic restraints of installation and upkeep.

Grease Interceptor Selection

There are a number of options to consider when you incorporate a grease interceptor into a commercial kitchen plumbing design. The most important design parameter is designing a system that will adhere to local building codes. The Plumbing & Drainage Institute (PDI G101) and ASME (A112.14.3-2000) have published code guidelines that are most widely accepted, though some local jurisdictions have amended these guidelines to fit their needs. It is also important to look for PDI's certification ensuring that the grease trap has been tested and meets the demands specified by the manufacturer.

Both PDI and ASME codes provide guidelines for sizing. Sizing is based on the assumption that all fixtures being served discharge simultaneously. There is much debate over whether this assumption is truly reflective of the demand placed on the grease collection device. There is little opportunity for all fixtures and floor drains to discharge simultaneously. The reason sizing is so important is that typically the larger the unit, the greater the capital and installation cost. Installation of a grease collection system can contribute a significant portion of the capital cost for a restaurant start up. Depending on the type of operation, higher overhead costs may in turn put strain on the profitability of the enterprise and would be an economic barrier for a new entrepreneur. Economic barriers, in turn, hurt the economy. IAPMO classifies grease collection devices into Grease Traps and Grease Interceptors. IAPMO references any collection device larger than 750 gallons as an interceptor.

Grease Interceptors

Grease interceptors are large units that typically have a cover similar to a manhole cover, and in most cases, are installed on the exterior of the building. Interceptors are available in metal, concrete and composite materials such as fiberglass. The advantages and disadvantages of metal are the same as those of metal grease traps. The advantages of concrete units are their availability and holding capacity. The disadvantage is that the units must be treated to resist breakdown. Concrete has a porous composition that disintegrates when exposed to animal fats and oils.(1) As such, concrete units must be internally lined with a recommended resin or membrane. And, concrete is susceptible to freeze-thaw deterioration in cold, wet environments.(1) If the unit is susceptible to cracking, the liner must not be compromised.

Interceptors manufactured from new materials such as fiberglass are now available. One such interceptor is the Proceptor manufactured by Green Turtle Technologies. Models range from 50 to 20,000 gallons and custom designs are available.

The advantages of large grease interceptors are their holding capacity and decreased cleaning frequency. Also, being located on the exterior of the building, cleaning can be done at anytime of day with little disruption to business operations. A disadvantages of a larger unit are the initial installation and capital cost.

Furthermore, large units are difficult to monitor and must be serviced by private waste/disposal handlers. It may be more economical for an enterprise to pay an employee to frequently perform maintenance on a trap rather than have an external service clean out an interceptor. It is important to note that if the interceptor is not installed within 10 feet of the last fixture it is servicing, grease buildup will occur in the internal plumbing system and increase maintenance costs. It is not uncommon for large operations to compliment their external interceptor with an internal grease trap located at the source of the heavier grease producing fixtures.

Center of main graphic: The Proceptor grease interceptor from Green Turtle Industries is an example of a fiberglass unit. Figure 1, above, is a diagram showing the grease removal process of Canplas Industries' thermo-injected polypropylene (plastic) grease trap.

Grease Traps

Grease traps are the most common devices used and have been in use for over 120 years.(2) Traps function by trapping grease in a system of baffles. Grease traps are compact, inexpensive and can be maintained internally by the restaurant staff, keeping overhead costs low. One disadvantage of traps versus interceptors is that their limited holding capacity requires the units to be cleaned regularly.

The most common traps are manufactured of metal. The advantage of a metal trap is its proven track record and long-established acceptance by the plumbing industry. The disadvantage of metal is its inability to combat corrosion caused by the collection of salt-laden grease. After a few years, the internal baffles rust out, and the unit no longer functions as it was designed. Typically, restaurant owners do not replace the units until years later when the external cabinet is compromised. One alternative would be a metal trap manufactured using stainless steel, though the disadvantage of stainless is its cost in relation to other alternative traps. New to the market are plastic grease traps that are corrosion resistant and lightweight for easy installation. Canplas Industries was the first company to introduce a unit made of thermo-injected polypropylene (Figure 1). The disadvantage of plastic is that its manufacturing technique limits the depth of sizes and the variety of dimensions for retrofitting.

Future Trends

Some counties and municipalities have reacted to the grease problem by requiring that large external interceptors be installed to protect municipal sanitary systems. This reaction does nothing to address establishments that do not maintain their grease "collection" devices. Regardless, if the device is a trap or an interceptor, the units will not function as designed once they are at capacity. As highlighted in an article by Max Weiss of Weiss Research inPM Engineer's February '03 issue reporting on the findings of the Orange County Grand Jury, few agencies have an inspection and enforcement program in place.

It appears this problem arises when assessing under which bureaucratic umbrella grease collection resides. In most cases, the municipal building departments govern installation. Monitoring is either not done or comes under the umbrella of the sanitation department. Unfortunately, resource constraints and a lack of communication between governing bodies result in inspection and enforcement slipping down the drain. I believe the Greater Vancouver Regional District of British Columbia, Canada ( has come up with an ingenious solution. While visiting the west coast earlier this year, I was introduced to their While visiting the West Coast earlier this year, I was introduced to their Code of Practice for Wastewater Management at Food Sector Establishments. The code has been the catalyst for the building, sanitation and health department banding together to ensure conformance. As part of the code, establishments must keep a record of all maintenance, cleaning and inspection carried out for a period of two years. Food preparation facilities are inspected on a regular basis, ensuring public health and safety. To capitalize on resource constraints, the health inspector, while at each individual location, ensures the logs are maintained, flow restrictors are in place and the equipment appears to be in working order. Failure to meet the code is then transferred to District Sewage Control for enforcement. Failure to meet the code may cause you to be served with a fine up to $10,000. For reoccurrence, the fine can be as much as $10,000 per day.

The Canadian Standards Association as well as the European Union are evaluating sizing and performance guidelines of their own. Benchmarking the EPA's Clean Water Act that regulates the grease discharge concentration to less than 100 ppm and solids to less than 350 ppm, the biggest challenge is to develop a reliable and consistent testing parameter to certify grease collection devices. System design and performance are also being evaluated. System designs include the incorporation of solids interceptors to enable filtering of fixtures such as food waste grinders and dishwashers not currently addressed by the codes. Also being analyzed is a bioremediation treatment system. Bioremediation should not be confused with enzyme supplementation. Enzymes are emulsifiers that displace the grease further downstream. Bioremediation is the introduction of bacteria to the grease effluent. In bioremediation, the bacteria breakdowns the grease similar to the process witnessed in a sewage treatment plant. Hunter Plastics, based out of London, England, has been complimenting its line of grease traps with its Biopak System. Biopak is a bacteria culture introduced via an automated pumping system or manually in the form of a powder. Results have shown that bioremediation improves the efficiency of the system and extends maintenance intervals.

The Solution

A grease collection system must be designed to meet performance criteria for the application and to balance the economic restraints of installation and upkeep If capital and overhead costs are of concern, a grease trap is an economical option, providing the owner is committed to the maintenance procedures recommended by the manufacturer. Let's face it, grease traps are not one of the most pleasant fixtures to clean. If you do not have the stomach it for it, bioremediation and/or a private contractor are a good alternative If an establishment is not limited by capital capacity and ongoing maintenance costs incurred through a private contractor are feasible, a grease interceptor is a convenient alternative.