Most Frequently Asked Questions

What is a Grease Trap or Interceptor?


Simply put, a grease trap is a receptacle that kitchen wastewater flows through before entering the sanitary sewer lines. This receptacle captures, or "traps" grease. How? Grease, the industry term for animal fats and vegetable oils, (FOG's) is 10 to 15% less dense, or lighter than water. Grease is also immiscible with water, which is to say it does not mix with water. Thus, grease and oils float on water. When kitchen wastewater flows through a grease trap, the grease and oils rise to the surface and are trapped inside the receptacle using a system of baffles. The captured grease and oils fill the trap from the top down, displacing "clean" water out of the bottom of the trap and into the sanitary sewer line. This is why you see a grease "mat" when observing a grease trap. When a significant layer of grease has accumulated, the trap must be cleaned out.

The three predominant grease traps found in foodservice operations are small passive grease traps, large pre-cast concrete grease traps, and Big Dipper® automatic grease/oils removal systems. In some areas, these traps are referred to as grease "interceptors".

Passive grease traps date back to 1885 when the first US patent was issued. Today's large and small grease traps use the same basic operating design as the 1885 model. While they do a fine job trapping grease, removing the grease is a task left to the owner. If the trap is a small passive trap, it must be cleaned out by hand. If the grease trap is of the large, pre-cast concrete variety, it must be pumped out by a professional with a vacuum or pump truck. The single most important aspect to understand is that, as a grease trap fills, its separation efficiency diminishes. When a trap is filled to capacity with retained grease/oils, there is no separation occurring and the trap no longer works. Since grease and oils fill a grease trap from the top down, it is frequently hard to measure the depth or fullness of the grease trap, making it difficult to know when it needs to be cleaned. Failure to clean the grease trap in time creates a considerable volume of business for pipe cleaners, and headaches for sewer systems and septic fields.

If the grease trap is a Big Dipper® Automatic Grease Removal System, the grease and oils are skimmed out automatically using a timer or sensor mechanism. The automatic grease removal process takes place daily in the case of timer-based systems and before the trap is 10 percent full in sensor-based systems. This automatic grease removal process relieves the owner of the burden of measuring grease levels and either hand scooping grease out of small passive traps or paying grease trap cleaning services to clean large traps.

The local water authority or council requires all waste water discharges to their sewer system to comply to an approved acceptance criteria.  See sample acceptance criteria.

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Why would I buy a Big Dipper® instead of a competitor's system?

The competitor's system is old technology and what the Big Dipper®  was like 20 years ago, so by choosing a Big Dipper®, you are buying the latest technology which is patented thus preventing others to copy . The Big Dipper® offers features and benefits like no other unit on the market which benefits the end user in terms of ease of emptying the grease container and ease of replacement of parts without draining the entire unit.

Please call us to find out more.


Big Dipper

Competitor's System

IP rating

IP 55 Rated by Australian Testing Authority

IP 66 rated by ?

Product Compliances

APPROVED  BY  USA Authorities - ASME, CSA, MEA,IAPMO & European CE.

The Big Dipper does not meet the requirements of BS EN 1825 because the 50mm inlet and outlet pipes cannot pass an 80mm ball. This standard was written for passive grease traps.

British Standard BS EN 1825-1 and 2

Grease removal rate

High capacity due to orientation of wheel and depth of internal baffle. Smaller unit required, less costly. Strainer basket large in capacity, less cleaning

Lower capacity, larger and more costly unit required.

Small strainer basket.


unit can be installed left or right handed

must be ordered, right or left handed. No flexibility for relocation


Heating element located within lid assembly

Heating element located within tank. The tank must be drained to allow element replacement


The inlet strainer basket can be removed without submersing hands in waste water.



Grease collector

OH&S design allows for no mess / no fuss

Small container, with cut out in lid, rubber hose connected to fill up

Research  and Development

Patented design  in 1972 [40 years ago] in USA. Unit has been upgraded consistently through constant R & D.

Current units shall allow updates in the future.

Old technology. copied in Ireland from the USA design 20 years ago.

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How does a Grease Removal System work?

The units operates in 2 stages, the grease entering the unit is trapped, then the unit automatically skims the trapped grease into a separate grease collection container. A controller controls the self cleaning operation activating the skimming wheel at the proper time. Cleaned water exits the unit and flows into the drain lines. Incidental solids in the kitchen flow are trapped in a strainer basket for removal. Ongoing maintenance is required - which consists of each day the internal solid strainer and grease container should be checked and emptied as required. Every 3/4 months the unit is required to be thoroughly cleaned by way of a wetvac to ensure all suspended solids and all components are clean with the timer being checked to ensure proper operation.

Purchasing is easy and you have the option of using Flexi Rent, a mini-lease program which is quick, easy and affordable.

A Flexi Rent plan is available upon request.

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Does the Big Dipper® Grease Removal System require Australian Standards Watermark certification to MP52-2005 or AS5200?

No, because under The Plumbing Code of Australia, (AS3500) and AS 5200, states that a Big Dipper®  Grease Removal System is not required to be Water Mark certified.

Endorsements and Approvals for Big Dipper® - Thermaco Point Source Grease Removal Systems.

Thermaco grease trap products are widely accepted and approved for use throughout the nation. If local code approval is required in your area, please contact us. Our products may already be approved. If not, we will make every effort to obtain approval in your area so that you can also benefit from Thermaco grease trap products!

Product Appraisal from WSAA (Water Services Association of Australia)
Product Appraisal Number TWA 0802.01 states that "it is recommended that WSAA Members and Associates, accept or authorise the Big Dipper Australia Pty Ltd range for use in sewer networks."


Accepted for Listing By:*
IAPMO (International Association of Plumbing and
Mechanical Officials)


Conforms to ASME Standards*
ASME A112.14.3
ASME A112.14.4

Canadian Standards Association Logo

Tested and Certified By:*
CSA (Canadian Standards Association) to comply with:
CAN/CSA-C22.2 No. 68-92
CAN/CSA-C22.2 No. 88-1958

Plumbing & Draining Institute Logo

Conforms To Plumbing & Drainage Institute Standard

NSF logo

Accepted for Listing By:*
ASME A112.14.3

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Why would I buy a Big Dipper® instead of an in ground grease trap?


The main features and benefits of a Big Dipper® Automatic Grease and Oils Removal System are:

  • A Big Dipper® Automatic Grease and Oils Removal System does not require any concrete cutting etc. as they are installed above ground and not installed underground.
  • Compact in size and can be easily retrofitted into an existing facility to avoid expensive business interruptions. Thus, no building owner permission required or where it is impossible to install a standard grease trap.
  • Can be removed easily from facility
  • No pump out costs and disposal costs. (In ground grease traps require pump outs every 3 months or less)
  • Produces yellow grease, by automatically skimming from the kitchen waste water
  • Recovered oils and grease are substantially water free and suitable for recycling. (Yellow grease)
  • Keeps all drains grease free
  • No rancid smells from decaying food.
  • No water used during cleaning
  • Construction is durable
  • Standard in ground grease traps produce brown grease which attracts vermin and smells because it is contaminated with food solids and water.
  • Yellow grease contains less food solids thus no decaying, rot or rancid smells.
  • The Big Dipper® Automatic Grease and Oils Removal System removes up to 98% of grease, oils and fats, as tested to ASME standards.
  • If your current trap is too small, A Big Dipper® Automatic Grease and Oils Removal System can be easily installed, to ensure ongoing authority compliance.

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What is the difference between brown and yellow grease?


Oils, fat, grease and food solids combined with water, within conventional in ground grease traps is known as 'Brown Grease'.
Brown grease attracts vermin and smells.

Oils, fat and grease recovered from Big Dipper® Automatic Grease and Oils Removal Systems is 'Yellow Grease'.

  • Yellow grease contains few solids and therefore does not cause decay or rancid odours.
  • Yellow grease also has a very low water content.
  • Yellow grease is preferred for recycling, especially Biodiesel.

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Selected articles from the Thermaco Blog

Grease Traps Helping Green the World

In the 1980s, the grease removed from restaurant grease traps, including automatic grease removal systems like Big Dipper® , sometimes was disposed into dumpster trash. At the time, many food service locations did not access to grease recycling services and dumped waste fryer grease, meat drippings and interior grease traps into their garbage waste. Today, nearly all food service establishments are serviced by recycling companies that collect spent fryer grease, meat drippings and grease trap waste. What led to this change? Answer: 1) Recycling restaurant grease waste into consumer products is now profitable and, 2) a network of grease trap pumping services sprang up to service the thousands of in-ground concrete grease separators installed during 1980- 2005 as a result of stricter sewer district requirements for new restaurant construction.

In 1985 there was virtually no biodiesel fuel production. Restaurant grease materials were used in cosmetic, soap and animal feed production with only the purest yellow fat materials acceptable for these uses. Grease trap fats had no recycling value. Furthermore, there was not enough consumption of yellow grease alone to justify higher profit margins. In the intervening years fats and oils consumption in consumer goods, including cosmetics, lotions, dog & cat feeds, cow & chicken feeds, as chemical feed stocks and biodiesel, has led to consumption driving higher prices which, in turn, has made recycling service companies financially healthy. Today’s better recycling economics enable nearly every food service establishment to have on-site yellow grease recycle bins and economically priced grease trap servicing by pumpers who increasingly take the brown grease trap waste to recycling centers.

Let’s define the terms yellow” grease and “brown” grease. Yellow grease is spent cooking oils from fryers, the meat drippings from cooking or left over butter or salad oil. Yellow grease has not come in contact with water but may have entrained solids such as breading, bits of food or other food related particles. Brown grease is fats and oils that come in contact with water such as grease trap waste. Rotisserie grease may be classified as either yellow grease or brown grease depending if the oven uses a water-filled grease collection pan. The same is true for wok ranges, combi-ovens, wet-type ventilation hoods and other kitchen appliances where grease and water mixes are created.

Higher fuel prices have made biodiesel an attractive energy alternative leading to numerous small and medium sized companies entering the biodiesel production business. The increased demand for fats and oils has made brown grease valuable. In addition to being convertible into biodiesel, brown grease is also being utilized to combust one state’s sewer sludge. Connecticut utilized the brown grease in over 7 million gallons of grease trap waste in its sludge incinerators. This “free” fuel enabled environmentally safe disposal of both municipal sludge and grease trap wastes.

Yes, grease traps have always protected the world’s sewer systems by catching food service establishment fats and oils. In today’s energy tight economy, grease traps also provide clean recycled energy source material for biodiesel fuel. Brown grease is now “Green”.

Effluent Grease Recovery – 21st Century Recyclable Product

Our great grandparents recycled meat drippings into soap. Today their great grandchildren recycle meat drippings and waste cooking oil into biodiesel, cosmetics, animal food additives and hundreds of other useful products. Included in the recycling equation are new systems for capturing and recycling kitchen drain water fats and oils.

The past forty years has seen the rapid rise of the restaurant industry. The proliferation of restaurants throughout towns has also created a serious problem: sewer line clogs caused by grease. Wichita, Kansas, a city of 350,000 population found 85% of their sewer line problems were caused by grease accumulation in the piping. As most food service facility managers already know, grease build-up within a building’s plumbing drainage system is also a major cause of sanitation problems. Effluent grease jeopardizes normal operations as well as creating health and safety hazards within the facility.

Increasingly, sewer districts are implementing programs involving financial penalties to make commercial kitchen operators conform to community standards. Grease separators are now being required and documented servicing is being enforced. Existing restaurants have difficulty retrofitting grease separators because of space, plumbing complexity and construction cost issues. Fortunately, there are newer technology products available to economically enable older facilities to meet community code standards. These new products fit into two categories: 1) automatic grease removal units and 2) compact supercapacity grease interceptors.

Automatic Grease Removal Units (GRDs)
These units are specifically engineered for the separation and removal of free-floating (non-emulsified) grease and oils from kitchen drain water flows. Most units are designed to fit beside pot-washing and dishwashing sinks to capture grease. These units are electrically powered and have a skimming and heating mechanism for daily removal of the captured fats and oils. For example, in a high volume hamburger restaurant, the removal of 7 to 10 pounds (3.2 to 4.6 kg) of grease by an automatic grease removal unit servicing the three- compartment pot-washing sink is typical. Because it is removed on a daily basis, the recovered grease is fresh, water-free and is suitable for recycling into biodiesel and cosmetic products. The grease is kept out of the facility’s piping, reducing maintenance costs and preventing costly downstream blockages.

Automatic GRDs offer the simplest installation and lowest operation costs with the restaurant staff routinely emptying the grease container and solids strainer basket. Annual electricity cost is usually less than $25.00. Automatic GRDs cost more than non-automatic grease traps, but pay for themselves in one to four years with lower maintenance and servicing costs. Additionally, many Automatic GRDs like the popular Big Dipper® have sanitary stainless steel and polymer construction which, can last three to four times longer than painted steel grease traps that eventually rust out and are prone to unsanitary stains.

Automatic GRDs are particularly suited to servicing very high grease effluent output cooking appliances like wok ranges, rotisserie ovens and combi-ovens. A high volume rotisserie oven may discharge 15 gallons (57 liters) of water and chicken drippings in one day. Typically, this liquid is 70% fat which means 10.5 gallons (40 liters) of pure fat can be profitably recovered while also saving the facility’s and the city’s piping from congealed grease. In these applications, an Automatic GRD may pay for itself in less than 6 months.

Compact Supercapacity Grease Interceptors (CSGIs)
Many sites have trench and other floor drain receptacles receiving flows from tilt kettles and other grease discharging appliances. There are other sites that do not generate much grease such as ice cream shops, downtown grills and sandwich shops but are required to have high capacity grease separators to protect the city’s sewer piping. With available space being a serious constraint, compact supercapacity grease interceptors are increasingly being installed in these sites. Supercapacity grease interceptors such as the Trapzilla® feature corrosion-resistant polymer construction and are small enough to be carried by two men through a commercial width doorway but large enough to hold 150 kg to 275 kg of retained grease. These supercapacity grease separators have evolved into product lines having solid separator modules, engineered designs that can be mounted between floors and site adaptable extension collars.

Recycling Pays in the 21st Century
The recovered grease from one high volume supermarket rotisserie oven may recover $7500/year in biodiesel grade fats. The recovered grease from a high volume hamburger restaurant’s pot washing sink may be worth $750/year and another $1200/year in avoided facility maintenance costs. With petroleum costs soaring above $100/barrel and predicted to reach $200/barrel in seven years (2015), capturing effluent grease becomes a profitable enterprise. Like our great grandparents, we, too, recycle waste grease for worthwhile products.

How We Came To Understand Thermal Inversion

Thermaco accidentally stumbled into an answer for grease trap thermal inversion. and, at the time, did not know it. In mid-2003 we were working on developing high capacity/small footprint grease separators capable of meeting the ASME A112.14.3 Standard. This is the separation efficiency and retention capacity certification standard for passive (non-automatic) grease separators. At the time, we were sending production product off to a third party testing laboratory and were failing to hold sufficient capacity to meet the Standard’s retention capacity requirement. This was particularly disconcerting because the products submitted had previously passed the test ten years earlier (the PDI-G101 test which is the predecessor test the ASME A112.14.3 Standard is based upon). Alas, we had no choice but to go to the drawing board and develop a new product design that would meet the A112.14.3 Standard.

To make a long story short, we evaluated numerous product designs and ultimately plowed new ground in the field of grease separator design. We went with a larger traditional design for our Big Dipper product and ultimately passed the test. I say ultimately as this will be covered at the end of this blog story. However, during 18 months of non-stop R & D testing work, we discovered a wholly new design that consistently retained more than twice as much grease and had a significantly flatter separation efficiency curve than our standard separator design. As this new design was unorthodox looking and did not integrate well with an internal strainer, we initially developed a semi-automatic sensor monitored concept called the Klearly™ with automatic solids transfer section. We went on to have this design third-party tested on the ASME A112.14.3 and PDI-G101 tests and discovered it held TWICE as much retained grease as our same size Big Dipper model with conventional separator baffling design. However, the Klearly’s unique product concept was expensive to manufacture and was never commercialized. Inside Thermaco we called this unique separator baffling design the AFI - Automatic Flows Interceptor, but with the decision to walk away from the semi-automatic sensor controlled unit, AFI was just another interesting, patent-pending design concept at Thermaco with no clear application use.

A few months later I was in California at a CalFOG meeting, a consortium of industry folks comprised mainly of sewer district pretreatment managers focusing on implementing effective programs to significantly reduce sewer system grease clog events (SSOs = Sanitary Sewer Overflows). The Pretreatment Managers went around the room discussing things their districts had done which had worked well at controlling food service facility effluent grease discharges to their sewer systems. Nearly all mentioned they had implemented installation of large, in-ground grease separators of 1000 gallon or larger capacity. When it came the turn of the Pretreatment Manager from San Francisco to speak, he painfully stated he did not have the larger in-ground 1000-gallon grease separator option. San Francisco, he explained, was laid out during 1850 - 1910, before the modern era and consequently, most food service facilities have no available space for 1000-gallon grease separators. He went on to say sewer grease clogging was a major problem, particularly in Chinatown, a restaurant intensive zone in one of the city’s oldest developed areas.

His comment triggered a thought. “What if we could take our new separator technology and make a super capacity passive grease trap which could fit through doorways and be installed inside restaurants in Chinatown?” A city with a problem seeking a solution and a company with solution seeking a problem was the genesis of Thermaco’s Trapzilla® product line, products designed for space constrained urban sites to replace smaller conventional grease traps and to provide sufficient capacity for convenient scheduled monthly pumping servicing.

What is interesting is Thermaco had a product design that retained 2X (we now have products that hold up to 3X) as same footprint size conventional grease separators, but we thought our design accomplished this because of superior lower tank flow dynamics control. It took a random telephone conversation to provide the true answer to why our design worked so well. Truthfully, we did not peg thermal inversion as being the causative factor until having a conversation in December 2005 with Stan Steinbach of EEC (Environmental Engineering & Contracting in Santa Ana, California - a recognized leader in researching and developing SSO management programs for Sewer Districts across the USA). Stan remarked our testing phenomena sounded a lot like thermal inversion and that he had recently heard an interesting presentation at WEFTEC (Water Environment Federation’s Technical Exhibition & Conference) by a speaker from WSSC (Washington Suburban Sanitary Commission) regarding separator grease loss caused by thermal inversion. Voila, the light came on and we suddenly understood why our new design works so well! Before hearing of thermal inversion, we thought our grease retention design improvements were primarily caused by better flow dynamics, i.e. reduced roiling motion inside the separator.

By concentrating on thermal inversion aspects, coupled with flow dynamic aspects (inlet & outlet weir design), we have discovered significant retention efficiencies can be obtained by designing to preclude thermal inversion effects. We now have separator designs that hold as much as 3X the capacity in the same footprint as conventional separators without affecting separation efficiency. Our Trapzilla® product line is based on AFI thermal inversion technology. Our soon to be introduced compact Big Dipper® line is also based on AFI thermal inversion technology, too. Although these products do not resemble each other in the least, they are indeed utilizing proprietary AFI design technology.

Back to the story beginning, we later discovered the third-party laboratory ASME testing apparatus was not built correctly to the A112.14.3 standard. Had it been built correctly, it is likely the original Big Dipper units would have passed the test and thus, the new AFI technology would not have been discovered. Trapzilla, the new compact Big Dipper series and the present center-module style Big Dipper platform would never have been produced. As the adage goes, “Necessity is the Mother of Invention” and our initial difficulties eventually led to new and much needed answers for sewer districts around the world.

Third Party Evaluations and Listings strong>


Approvals and Listings


Further listings/approvals are available upon request. Please contact Thermaco, Inc. for information.

* Please consult Thermaco for details on the specific models tested, certified, and/or listed by these organizations.