Passive Grease Traps - Landfill

Passive grease trap must be pumped out regularly, in turn significantly contributing to landfill waste. Passive Grease traps do not stop near 100% of the fats, oil, and grease from entering the sanitary sewer system and causing further grease blockages and raw sewage spills. Passive grease traps have a terrible odour from rotted food and grease waste. Passive grease traps are one of the biggest flaws in restaurant operations. This page will explain all aspects of the passive grease trap and grease interceptor including the chore of grease trap cleaning and maintenance.

Passive Grease Traps - Introduction

Passive Grease Traps and Grease Interceptors are metal or plastic tanks required in foodservice facilities to prevent fats, oil, and grease from entering the sanitary sewer or septic system. Grease interceptors are large in-ground outdoor tanks that (usually cement or fibreglass) trap grease and food solids from foodservice kitchen facilities.

Conventional Grease Traps are referred to as passive grease traps and gravity based grease traps. Grease Traps were originally designed over 100 years ago. Passive Grease Trap technology has remained virtually unchanged since the 1880's.

Over fifty percent of all sanitary sewer overflows in Canada and the USA result from grease blockages. What is the cost of a raw sewage spill?

Wikipedia has a great definition of grease traps and grease interceptors.

Grease Trap Contents

Animal fats, bacon grease, vegetable oils, vegetable fats, butter, margarine, cream, ice cream, sauces, lard and food solids are typical contents of a grease trap. Grease and water do not mix together (immiscible). Grease is between 10-15% lighter or less dense than water depending on the grade of oil and fat (Canola, soya, peanut, saturated, unsaturated). Fats, oils, and grease (FOG) float in water. Food Solids sink to the bottom of the interceptor.

Kitchens without Deep-Fryers still require grease traps

How Do Grease Traps Work?

Restaurant wastewater enters Grease traps from sinks and automatic dishwashers. The grease trap tank acts as a reservoir holding the wastewater and food solids that enter the trap. As the wastewater cools, the fat, oil, and grease (FOG) harden and the food solids settle. The FOG, being lighter than water, floats to the top of the grease trap. The wastewater is forced through the grease trap and out to the sanitary sewer. The FOG and food solids remain in the tank, increasing in volume daily. The FOG layer floats to the top. Food solids and grease sludge (brown grease) settle to the bottom of the grease trap.

If you take a bucket of cool water and pour in FOG, the FOG will float to the top of the bucket and harden. A grease trap functions in the same manner. Fats, oils, and grease fill a grease trap from the top of the trap to the bottom of the grease trap. The FOG fills the grease trap from top down, displacing the wastewater from the middle of the grease trap and into the sanitary sewer or septic system. In-ground grease interceptors work in the same method but at a larger scale. Grease Trap Top = FOG , Grease Trap Middle = Wastewater, Grease Trap Bottom = Food waste

Grease waste (brown grease) in a conventional grease trap is difficult to measure. Grease traps must be disassembled to view the level of waste inside the trap. Grease traps are required to be emptied or pumped out when the grease sludge occupies 25% of the tank. By-law enforcement have tools that measure the content levels of grease traps.

Passive grease traps emit Rancid Odors from Rotting Food and Grease Waste. The Smell is just plain nasty.

Grease Trap Design Flaws

Grease Traps were never designed to stop 100% of the grease from reaching the drain. A well maintained grease trap allows 15% of the grease in the wastewater to perpetually flow into the sanitary sewer. Grease traps at full capacity discharge 100% of the restaurant grease and wastewater into the drain. When a grease trap is full of grease sludge the trap is incapable of capturing any grease or food solids.

Passive grease traps and grease interceptors do not control the inflow of restaurant wastewater. During busy automatic dishwashing and sink draining periods restaurant grease bypasses the grease trap. Conventional grease traps do not have enough time to separate the FOG from the wastewater (retention time). The fast outflow of wastewater from automatic dishwashers allows FOG to bypass the grease trap completely.

Grease Sludge (Brown Grease) inside a passive grease trap is not visible and difficult to measure.

Grease Trap Maintenance

Is grease trap maintenance on your restaurant check list? Regularly scheduled grease trap maintenance must be established by restaurant management or ownership. The foodservice industry is known for their high employee turnover rate. Grease Trap maintenance must be the responsibility of management, not only performed when a dish washer feels like doing it. Grease trap / grease interceptor maintenance must become habit in a food service establishment. Staff absenteeism, business loss, and restaurant closures will be prevented with a grease trap maintenance plan in effect.

Drain snaking, Line jetting and Powerjetting are common grease trap maintenance expenses. These procedures occur when the plumbing between the grease trap and the sanitary sewer becomes stopped with grease blockages. Linejetting and powerjetting is forcing water down the pipes at high speeds pushing the grease into the sanitary sewer. Grease traps maintenance is frequently performed when grease traps leak or overflow. Rancid grease trap odours stem from brown grease and food solids that rot inside grease traps for weeks at a time. Regular Grease Trap Maintenance requires grease trap pumping and/or grease trap cleaning.

Grease Trap Maintenance - Never Use Grease Trap Bacterias or Chemicals

Grease Trap Pumping

Grease trap pumping is having a large pump and tank on wheels come to your foodervice facility. The truck, equipped with a large tank, brings the hoses inside the facility to the grease trap. The complete contents of the grease trap are pumped back into the truck's tank. In-ground grease intercptors are pumped outside of the building. Grease trap or grease interceptor pumping is typically performed when rank odours or grease blockages are discovered.

Passive Grease Trap Materials

Maintaining a clean and sanitary kitchen is a perpetual task. Stainless steel counters, sinks, dishwashers, and exhaust are a few of the standard stainless steel products in a commercial kitchen. Inexplicably, Grease Traps are made of steel, fibreglass, PVC and plastic. Rusted, leaking, or cracked grease traps cannot be easily repaired. Rusted grease traps must be replaced. Gasket and baffle repairs are frequent on conventional grease traps. Polyethylene or poly grease traps were designed and engineered to outperform other plastic materials. Common for mechanical stress in a polyethylene fixture is where a hole is cut to connect pipes, gaskets, and fittings. Polyethylene does not readily biodegrade. Polyethylene products remain in landfill for hundreds of years. Polyethylene, though a strong chemical composition, does become brittle over time. A grease trap company selling Polyethylene grease traps states that their grease trap products are guaranteed not to corrode, chip, peel or leach. Poly grease traps do not guarantee grease traps from cracking.

Stainless Steel never rusts, splits, or corrodes

Passive Grease Trap Manufacturers

Canplas, Watts Canada, Zurn, Ashland, Dormont, Green Turtle, Organic Resource Management Inc - ORMI

Passive Grease Traps must be maintained on a schedule. Monthly pumping is required for all passive grease traps and grease interceptors.

In-Ground Grease Interceptors

Grease Trap Interceptors are frequently sized at 150 Gallon or 200 Gallon Units for restaurant use. Grease interceptors are tanks made of PVC or Fibreglass that hold the fats, oil, grease, and food solids. The interceptor tanks are usually buried to the exterior of the restaurant.

To install a grease interceptor a large trench must be excavated. A cement footing is built to support the grease interceptor. The interceptor is placed within the trench. Pea Gravel (3/8 inch gravel) is poured into the trench to occupy the space between the earth and the grease interceptor. A second cement slab is required at ground level. The cement slab at ground level is anywhere between 18 to 30 inches above the grease interceptor for various levels of support and potential traffic.

Part of the required install of a grease trap interceptor is an extension collar to connect the access hole at ground level and the grease interceptor approximately 30 inches below ground level. The access hole fitting is removed when the grease interceptor is pumped out. Approximate dimensions of a 200 Gallon grease interceptor are 65 inches (width) X 40 inches (height) x 32 inches (Depth). In total, with extensions a grease interceptor will sit between 70 and 80 inches below ground level. Grease interceptor pumping is a permanent on-going monthly expense. A 1500 Gallon in-ground cement Grease interceptor is pictured above.

Excavation costs, equipment rentals, cement slabs, gravel, labour costs, and the Grease Interceptor Installed