Grease. When food is prepared in that little Mom-and-Pop diner down the street, at a four-star restaurant, or in the kitchen of a hospital or prison, grease happens. A lot of fat, oil, and grease. 
   Anyone who started out their working life asking, “Do you want fries with that?” has an inkling of how much of the slippery stuff a fast food franchise can crank out in a day. Imagine the volume of FOG (fat, oil, grease) an entire nation of restaurants and commercial and institutional food service can produce, and you’ll get a sense of how serious the job of keeping this sludge out of our water and sewer treatment systems has become. Removing FOG before it can reach these pipelines to these facilities becomes more critical every day.
   On the front lines, this dirty job falls to the “grease interceptor”—the last line of defense between us and a virtual ocean of FOG. This month we talked with experts in the field about how grease interceptors work, where and how they are used, and the implications to public health and the environment of how these products are selected, installed and maintained.
   Sharing their expertise are: Ben Ismert, president of Schier Products, New Berlin, Wis., manufacturer of Trapper II, Great Basin and Foglifter lines of grease interceptors; Silvano Ferrazzo, the business development manager for Green Turtle America in Charlotte, N.C., manufacturer of Preceptor grease interceptors, PHIX water treatment, and interceptor monitoring/alarm systems; Chris Rylant, the senior business engineer for Jay R. Smith Manufacturing Co., in Montgomery, Ala., which produces grease interceptors, Grease+Gard recovery devices and treatment systems; and Craig Swider, the product manager for Josam in Michigan City, Ind., whose products include a line of grease interceptors and sensing alarms.
   The first order of business was to ask the members of this month’s panel a simple question: How does a grease interceptor work? The answers we received were many and varied and, taken as a whole, provided more information than could be published in a single issue of Reeves. 
   The basics, however, were left to us by Irish-born mathematician George Gabriel Stokes and his work with the properties of fluids. In 1851, Stokes’ Law came into being. Simply put, Stokes’ Law proves that—in water—materials heavier than water sink and lighter materials rise. 
   Gravity grease interceptors take advantage of this concept by allowing grease, which is lighter than water, to rise to the surface, and the heavier sediment to fall to the bottom of the interceptor. A properly engineered grease interceptor allows sufficient time for this gravity separation to take place, and maximizes the separation by minimizing flow turbulence and optimizing fluid dynamics in the interceptor. Once the separation has taken place, the clarified water can then flow by gravity to the sanitary sewer system, leaving the grease and sediment behind in the interceptor for later removal by a qualified maintenance company. 
   Hydro-mechanical grease interceptors are designed to utilize this natural separation process, aided by a flow-control device and a series of internal baffles to accelerate the separation process and therefore utilize a smaller overall tank size. As the grease, fats and oils, rise to the top of the wastewater inside the collection chamber of the interceptor, they are captured and held within the collection area of the grease interceptor. The wastewater—rid of at least 90 percent of the grease, fats, and oils—exits the interceptor leaving separated FOG trapped within the collection chamber.

RJ: Are there different types for different applications?

Josam Products: The Plumbing and Drainage Institute establishes a standard. Within that standard there are roughly 50,000 point-of-use interceptors sold within the United States per year. Point-of-use manual grease interceptors are installed within the building. The next category is large, pre-cast interceptors installed outside the building, which account for a comparable number of units because in some regions they are only units allowed. Grease removal devices are located within a building; they capture the grease and remove it to an attached or detached storage tank depending on local municipal regulations.

Green Turtle America: There are several types of grease interceptors and grease traps, not so much for different applications, since they are all supposed to separate grease, but for different plumbing codes or design restrictions. For example, in most Western states, the Uniform Plumbing Code requires one design of grease interceptor, whereas the International Plumbing Code allows a different design. The Uniform Plumbing Code has identified different types as: Gravity grease interceptors; hydro-mechanical grease interceptors, previously called under-the-sink grease traps; grease removal devices; and FOG disposal systems.
   In addition, food service establishments may be limited in the design they can use due to space restrictions or physical location. For example, some historic areas do not allow outside burial. Some areas also allow the use of under-the-sink grease traps where space might be a limiting factor. The latter can use gravity separation or some combination of gravity, mechanical, or electrical heating and skimming grease removal devices and FOG disposal systems.

Jay R. Smith: There are two basic types of grease interceptors, gravity and hydro-mechanical. However, there is an abundance of different styles, options and variations available today for these two types of interceptors. Mostly these variations have to do with how they are installed and what is done with the grease once it is captured. Basic hydro-mechanical units can be designed to sit on the floor, be recessed into the floor usually requiring an extended top; or be recessed into a steel cradle. There are low types that are built wider and longer than normal, but not as tall, to sit underneath a counter or cabinet. 
   There are semi-automatic units with manual draw-off mechanisms where hot water and water pressure are used to force the grease out of the interceptor when cleaning. There are fully automatic units that use heaters and mechanical skimmers to remove the grease from the interceptor and into a furnished container using an automatic timer. Finally, there are bio-mediation units that use bacteria to eat the grease while it is captured within the interceptor. There are all types of units available depending on the desires and available funds of the business owners.

RJ: Where and how is each type of interceptor commonly used?

Schier Products: Interceptors are used anywhere the local code or jurisdiction requires that greasy waste cannot enter the public sewer system. This includes restaurants, schools, and hotels—anywhere there is a kitchen sink/food prep area with the exception of residential kitchens. The interceptor should be located as close as possible to the grease producing fixture. Indoor interceptors can be of three types: hydro-mechanical grease interceptors, grease removal devices, and FOG disposal systems. HGI use some sort of flow control device and baffle system. 
   A grease removal device is an interceptor, usually an HGI that has an additional feature: It transfers separated grease into a separate container, which then gets emptied into specific containers for proper disposal/recycling. A FOG disposal system is typically an HGI that also incorporates an additional media, biological being the most common, that further enhances grease separation efficiency.

Green Turtle: Plumbing and building code requirements can primarily drive what type of grease interceptor is used in which region of the country. Grease interceptors historically have been large—500 gallons and up—and buried outside in the ground. In large institutions, they may have multiple units. For food service establishments, interceptors can be buried in the ground outside the building, in the basement, under the sink, above the floor; buried in the floor in the kitchen, suspended from the ceiling under the kitchen in a multi-level buildings; and above ground, where the waste water is pumped into them and then the clarified water flows by gravity to the sanitary sewer.
   At fast food restaurants, fryer grease, also called “yellow” grease, is segregated and won’t go into the interceptor because it’s a valuable commodity that can be reclaimed and recycled into products like bio-diesel fuel. “Brown” grease is what’s stored in the interceptor tanks.

Smith: The gravity-type unit is almost always installed outside. These are normally large capacity concrete, steel or fiberglass units. They do a good job of collecting the grease and protecting the city’s sewer system if they are maintained properly. There are also very large fabricated steel hydro-mechanical units that generally have to be put outside. The problem with these units is that they are often so far from the kitchen fixtures that grease often cools and solidifies in the piping before it reaches the grease interceptor, causing problems for the building owner. 
   We recommend, where possible, to install the smaller hydro-mechanical point-of-use grease interceptors right at the fixtures inside the kitchen where most of the grease can be intercepted prior to entering the drainage system. As for most of the specialized units mentioned above, they are mostly hydro-mechanical point-of-use units.

RJ: How do grease interceptors fit into the “green” plumbing picture?

Schier: Currently, many grease interceptors are made of fabricated steel or pre-cast concrete. While most manufacturers have superior coating methods, today’s chemicals and maintenance practices make quick work of these coatings and lead to interceptor leakage and failure. Interceptor failure can lead to ground water contamination, kitchen food contamination, and/or hazardous sanitary sewer overflows. The wasted materials and energy to replace these failed units is definitely not green, not to mention the environmental hazards. 
   There are some manufacturers using materials, such as thermoplastics, that do not corrode, solving many of the above-mentioned problems. In the future, we see a strong market demand for not only non-corrosive materials, but materials with high post-consumer (recycled) content.

Josam: We only have one planet and we need to be aware of where that waste water is going. Grease that enters a municipality’s sanitary pipe system sets off a chain reaction by reduced capacity of the drain pipe, slower water flow, and eventual blockage of the line. This can lead to damaging, upstream flooding. The expenses incurred by both the municipality and the property owners can be greatly reduced by the proper removal of grease at the point of source. Elimination of grease-laden pipe systems will also reduce the amount of water utilized to clean such lines. 
   One of the components of much new construction (especially in LEEDS buildings) is that they want to keep everything that is produced on that site on the property. For example, a lot of building require retention ponds if it rains. The same applies to the FOG produced. From another side, our units are typically made of a steel product that has been and can be recycled.

Smith: Grease is more or less a hazardous waste when allowed to enter the drainage system. Once it enters the drainage system, it is very hard to remove and dispose of properly. Therefore, preventing as much of it as possible from entering the drainage system is very good for the environment. In addition, if it is collected prior to entering the sewer system, it can be recycled into useful products such as soaps, cosmetics and animal feeds.

Green Turtle: Some newly available engineered grease interceptors can fit well into “green” initiatives or sustainability, especially when compared to some older style grease interceptors that are made of concrete. Some engineered grease interceptors such as Green Turtle’s Proceptor™ systems are manufactured with fiberglass and are not prone to the corrosion or failure due to cracking observed in older concrete interceptors. Since the fiberglass interceptors last longer, (some are guaranteed for 30 years), they do not need to be replaced, saving valuable resources and energy. In addition, the fiberglass can be recycled. 
   Newer technology means that grease and sediment are removed and stored more efficiently, which means that the sanitary sewer system infrastructure is preserved from damage and corrosion associated with grease build-up, and there is less load on the POTW (Publicly Owned Treatment Works Waste Water Plant) to treat grease waste. So, it’s better for the environment.
   In older concrete interceptors that have not been well maintained or designed, grease builds up in corners and on the interior concrete porous surface. In this stagnant environment, anaerobic bacteria feed and create hydrogen sulfide gas which is harmful to humans. As the bacteria multiply, the water can become acidic and cause corrosion in the interceptor, associated piping, and the sanitary sewer system infrastructure. Newer engineered interceptors minimize those types of problems, and are therefore better, or greener, for the environment.

RJ: What is important for plumbers to know about grease interceptors?

Schier: Without proper installation per the manufacturer’s instructions, the interceptor will not perform well. The most commonly abused installation practice is not installing the flow control device, if applicable. Also, without proper and thorough routine maintenance, no interceptor will separate grease effectively. Many plumbers know this, but forget to emphasize this to their customer (the owner), once they leave the job site.

Josam: The plumber must understand that the proper installation of a manual grease interceptor will not ensure that the interceptor will prevent grease from bypassing the unit. The interceptor is designed to retain grease up to its rated capacity. Failure to clean the interceptor at this time will lead to grease bypassing the unit. Since the manual interceptor is a “closed box”, knowing when to clean the unit is difficult to determine.
   Josam produces the SAP Sensing Alarm Probe which measures the amount of grease retained in the unit. The probe sends a wireless signal to a wall-mounted controller which notifies the end user to open the sealed cover and remove the grease before its rated capacity is met. The SAP is available on all Josam’s manual grease interceptors and can also be retro-fitted into existing interceptors. 
   Since the removal of grease is a messy job and reluctantly performed, Josam also offers the 60100H-GRD which pumps the grease retained in the interceptor at programmed intervals or the 60300A grease recovery device which utilizes the SAP probe to measure the grease retained in the interceptor and automatically pumps the grease to a reclaim tank.

Smith: First, the hydro-mechanical units must be installed properly with the flow control fitting installed and vented. Second, they must all be maintained properly according to the manufacturer’s instructions and the grease must be disposed of or recycled properly. Most all grease interceptors work great if they are properly maintained. The problem is, unfortunately, that most are not maintained properly, if at all.

Green Turtle: The first thing a plumber needs to remember in the case of a grease interceptor is that bigger is not necessarily better. A properly designed grease interceptor system needs to take into account what is coming into it, and what effluent quality or treatment level is needed. Although a larger grease interceptor will allow more time for gravity separation, if it is too large, the contents will quickly stagnate and become septic, leading to harmful hydrogen sulfide odors, and corrosion. Larger grease interceptors (over 3,000 gallons) also are more difficult to pump out and clean. 
   The Uniform Plumbing Code recently recognized that bigger is not better by moving away from old sizing methods which resulted in large interceptors being used. New sizing formulas being adopted mean smaller interceptors, less odors, less corrosion. 
   Secondly, plumbers need to remember that older is not necessarily better. They need to be open to new design ideas, and to work closely with grease interceptor manufacturers to properly install the correctly sized and designed interceptor required for the project. Just think how much easier it is to maneuver and install a 1,000-gallon fiberglass interceptor that weighs 800 pounds, vs. a 1,000-gallon concrete one that weighs over 40,000 pounds. 
   Thirdly, grease management is like a three legged stool: (1) A correctly designed, sized, and installed grease interceptor; (2) regular maintenance and cleaning of the grease interceptor to prevent excessive grease and sediment build-up and maintain effluent compliance, and (3) a well-trained kitchen staff that minimizes excessive amounts of waste oil and grease from going down the drains and into the interceptor.