Understanding Grease Traps and Kitchen Sinks

Understanding Grease Traps and Kitchen Sinks

Quick guide for commercial kitchen managers and restaurant owners.

You might think that pouring any type of liquid down the drain should be fine, as long as solid food does not block your plumbing, but that kind of practice gets numerous commercial businesses like cafés and restaurants in hot water.

One of the first things you should know if you’re in the foodservice business is that not all types of fluids should be drained down the kitchen sink. Pouring fats, oils, and grease (also known as F.O.G) down the drain should be avoided at all costs. Otherwise, getting rid of solid wastes would be the least of your problems in kitchen maintenance.

Fats, oils, and grease will clog your sewer lines and create issues in water treatment facilities. Not to mention, it can also block your commercial property’s waterways. In order to deal with fats, oils, and grease, one of the most helpful tools you can get are grease traps and grease interceptors.

New South Wales’ Water Management Act, 2000

In its bid to safeguard water sources, the NSW government passed the Water Management Act of 2000. This act seeks to establish water management principles and enforce a water management outcomes plan in the State.

Section 91C of the Water Management Act 2000 requires all entities dealing with properties having drainage systems to get a license before building the drainage system; otherwise, the person is not authorised and is guilty of an offence.

In addition, Section 26 requires the management plan to identify existing drainage works in the area and review how these are managed, including restaurants and other commercial properties. This means that the permit of the commercial property to build its own drainage system could be disapproved without a good and working grease trap and drainage system.

What are Grease Traps and Grease Interceptors?

What are Grease Traps and Grease Interceptors?

Grease traps have been around for hundreds of years. The fact that many are still using it today shows how effective they are. However, most grease traps nowadays are more functional —especially those used in commercial facilities. The terms “trap” and “interceptor” are often interchangeable. But generally, people refer to smaller equipment as “grease traps” and larger systems as “grease interceptors”.

How Do Grease Traps and Grease Interceptors Work?

Grease traps and grease interceptors are plumbing devices designed to trap solids and most greases before they go through wastewater disposal systems. This filtering system ensures that only water (with a minimal amount of oil) is allowed to enter wastewater facilities. After this, the water will enter septic tank treatments facilities for further processing so they can be reused again.

How Do I Choose Commercial Grease Trap?

If you are looking for the best grease trap or grease interceptor for your commercial property, here are the main considerations:

  1. Determine Wastewater Contents
  2. Determine Trap Size
  3. Type of trap installation
  4. Number of meals generated per day
  5. Hydraulic load

Determine Wastewater Contents

  • Does your wastewater usually contain remnants of fat, grease, or oil?
  • Are there times when bits of solid food get through your filtering system?
  • In terms of substance ratio, do your wastewater contain more fat, grease, or oil?

These are the questions one should ask when deciding on what type of grease trap to get. Depending on your answer, you should get a grease trap that works well with the type of substances often found together with your wastewater.

Determine Trap Size

  • Is your food-related business a small-scale operation, or does your business cater to hundreds of people a day?
  • Are you planning on keeping your business small and limited, or would you be gunning for expansion in the future?

When you answer these questions, you’ll be able to check how big your grease trap or interceptor should be. For a small-scale business, a small to medium-sized grease trap system would do. However, for big commercial operations, you should make sure that your grease interceptor would be able to accommodate the F.O.G you generate on a daily basis.

Type of trap installation

Grease traps and interceptors can be installed as a free-standing unit or underground. Usually, grease traps are installed under the sinks of restaurants. They can be as small as a basic box or as big as a mini fridge.

On the other hand, grease interceptors are bulkier units that often take up a lot of space. Larger-scale restaurants and food courts usually use large interceptors. Due to their size, grease interceptors are often placed underground or outside the building as free-standing unit.

Depending on the size of your food-related commercial property and the amount of space you have, you may choose a smaller-scale grease trap installed under your sink or a large-scale grease interceptor installed underground or outside your building.

Number of meals generated per day

Another factor to consider should be the number of meals your restaurant makes per day. Knowing this is helpful, as it allows you to estimate the volume of water that needs to be treated from your property. From there, you can select the right size of the grease trap or grease interceptor for your commercial property.

Hydraulic load

You should also check out the flow rate your kitchen equipment discharges. To be safe, check on the maximum flow rate of your equipment and select a grease trap that would be able to handle that hydraulic load. That way, your grease trap wouldn’t break down earlier than expected.

With these factors as your guide, you’ll be able to select the correct type of grease trap or grease interceptor for your commercial property.

Which Systems Should Be Connected to Your Grease Trap?

Which Systems Should Be Connected to Your Grease Trap?

For a commercial kitchen, you should try to connect all of your sinks and systems to a grease trap or grease interceptor. As a restaurant or a food-service business, you are responsible for the wastewater you produce within your property. Therefore, you should ensure that the fats, oils, and grease you generated are dealt with appropriately.

Here are some of the systems you should connect to your grease trap if you are running a food-related business in a commercial property:

  • All sinks
  • All garbage disposal units
  • All floor drains
  • Dishwashers


Of course, the first thing you should connect to your grease trap is your sink. A smaller restaurant may just have one kitchen sink, while larger restaurants could have three or more kitchen sinks. As the person in charge of your operations, you should ensure that all your sinks are connected to your grease trap or grease interceptor.

Aside from food waste and water waste directly coming from food preparation, the contents of your mop and floor sinks also contribute to the quality of your wastewater. So, ensure that all sinks within your property are connected – from your kitchen sink and floor sink to your front-end sink. This helps prevent all types of build-up in your pipes.

Garbage Disposal Units

The more food you produce, the more food waste you are going to generate. Generally, kitchens have rubbish disposals where leftover materials and food are thrown. When you throw away food into these rubbish disposals, you do not just collect solid food. You also get to have a build-up of grease, oils, and fat.

If possible, try to create a system that connects your rubbish disposal for greasy waste to your grease trap or interceptor. That way, even with accumulated FOG, there will be no need to take drastic measures to get rid of accumulated food waste material in your plumbing.

Floor Drains

Sometimes, you cannot avoid being messy in the kitchen. Accidents like oil spills and food falling down the floor are hard to avoid. When that happens, you always have to clean up as soon as possible so that your kitchen would function back to normal.

But once you wipe or hose down the oil and mop the floor, you drain the water on the floor drains. You have to remember that the floor drains are also directly connected to your wastewater source. Without a grease trap, the oil and grease from the clean-up might end up going straight to wastewater treatment facilities.

By connecting a grease trap on floor drains, you also make sure that you trap the FOG from the water used while cleaning your restaurant.


This one is more of an optional choice. Some people believe that connecting your dishwasher to a grease trap is effective. Others believe that it could end up being more of a problem than a solution for you.

When using dishwashers, you often do a pre-wash to remove the significant food waste from your plates. However, no matter how well you did your pre-wash, there’s always a chance that leftover FOG will still be on the surface of your dining plates and serve ware. With a grease trap connected to a dishwasher, you will be able to directly trap the grease and oil that comes from the wastewater of your dishwasher.

Others believe, however, that the high-temperature water that comes with chemically emulsified oil can be dangerous for your grease trap. It’s always better to approach a properly licensed plumber when curious about whether you can and should connect your existing commercial property water waste systems to grease traps and interceptors.

How Do I Make Carry Out Grease Trap Maintenance?

How Do I Make Carry Out Grease Trap Maintenance?

A grease trap is an effective tool to avoid clogs or blockages. As a responsible manager or owner of a commercial establishment, you should properly clean and maintain your grease traps on a regular basis. Here are some ways to help make your grease traps long-lasting:

  • Reuse cooking oil, where possible
  • Remove extra food from plates
  • Regularly clean and clear the grease trap

Reuse Cooking Oil, Where Possible

Don’t throw and discard oil that can still be used just because you have extra. Apart from wasting money, you’ll also lose time and resources when you fail to maintain your existing grease trap system.

Try to reuse oil that you’ve used before. By doing so, your grease trap would have less oil to deal with, and you’ll have more to use either for cooking or biofuel.

Remove Extra Food from Plates

Food can lead to blockages, so make sure to remove these before you throw your wastewater into grease traps. While some grease traps have filters for solid food, these accumulate fast and could lead to drainage issues. Avoid facing this problem by getting rid of extra food waste before draining your wastewater.

Regularly clean and clear the grease trap

To avoid grease trap spill overs, make sure to habitually clean and clear your grease trap. Check your grease trap – if it’s already a quarter full, the FOG has built up steadily, and you need to get rid of these before you use your grease trap again.

Trust Green Planet Plumbing for All Your Commercial Newcastle Plumbing Concerns.

Grease traps are effective tools used to maintain the quality of wastewater going into Hunter Water in New South Wales and all commercial properties that deal with food preparation and food making are required to have grease traps in their kitchen in order to avoid issues like clogs and overflows.

If you are currently experiencing issues with your plumbing and you suspect that it’s related to grease traps, clogged drains or blocked sewers, contact Green Planet Plumbing so we can look into the issue right away. Having issues on drains and clogs again and again will definitely take its toll on your business financially — not to mention the wasted time and resources.

Contact Green Planet Plumbing

Do not hesitate to reach out to Green Planet Plumbing. We are a dependable team with years of experience under our belts. We constantly fix blocked drains and sewers to get them flowing again and that means we can confidently help fix these issues for you.

To find out more about us and our values, visit us online at greenplanetplumbing.com.au. Alternatively, contact us today by calling us on (02) 4911 9402 or emailing us at mailto:hello@greenplanetplumbing.com.au and let us know how we can help.