Grease Traps

Disposing properly of used fats and oils is very important. If you don’t, they can cause expensive problems later. Fats will become solid and eventually block your pipes requiring a plumber to clear. This can also happen to the Council’s pipes and pumping stations and at the sewage treatment plants.

To stop blockages Clutha DIstrict Council requires you have a system installed to remove the fats and oils from your wastewater. These systems are often referred to as ’grease traps’.

There are two types of grease trap. Each has its own installation and maintenance requirements. You will also require formal consent from the Council to operate your grease trap. This consent will outline the things you need to do to make sure your grease trap is working well.

Types of grease traps

Passive grease trap

These are normally found outside your premises. Located in the ground, they are often covered by metal plates. Passive grease traps work by cooling down the wastewater causing the fats and oils to float to the surface of the water. Other solid material, such as food scraps, sinks to the bottom of the grease trap.

The fat on top and the solids on the bottom of the grease trap need to be removed regularly. This is done by sucking up the entire contents of the trap. At the same time, the inside of your grease trap should be hosed down to clean the sides.

After cleaning, the grease trap must be filled with cold water, so it is ready to work again. Cleaning the trap should be done regularly – once a month is usually alright, but it will depend on your type of business and how much fat is going into the grease trap.

You need to maintain a cleaning record for your grease trap. This should be kept on your property and shown to an Environmental Health Officer or Trade Waste Officer if requested during an inspection.

Mechanical grease separators

Mechanical grease separators are found under a bench inside the kitchen. They work by skimming liquid fat from the surface of the wastewater inside the separator. A heater inside the separator ensures the fats and oils form balls which are collected by the skimming wheel. The fats and oils are drained into a container on the side of the separator.

The fats and oils can then be collected along with other used fats and oils for recycling or be disposed of along with other food waste. This container should be emptied every day.

Fats, oils and greases (FOGs) are an essential part of almost all food businesses. They are used as ingredients and for cooking purposes. FOGs residue is also left on plates and cooking utensils which, when cleaned, transfer into the sewage (public wastewater) system.

Proper disposal of FOG’s is important, otherwise problems will be experienced later on as fats solidify and block sewers – these are sometimes known as ‘fatburgs’. This can occur at any point on its way to the Wastewater Treatment Plant (WWTP), including at the WWTP itself, resulting in a lower quality of wastewater treatment. Treated wastewater is discharged into the environment, so quality of treatment is important.

To prevent blockages and WWTP problems, Council requires all food businesses/premises engaged in the cooking, preparation or sale of food (e.g. restaurants, takeaways, hospitals, hotels, bakeries, butcheries and supermarkets) to install and regularly maintain a system that removes FOGs from the wastewater discharged from that business.

You can reduce the amount of cleaning and maintenance on your grease trap by following some good housekeeping practices including.

• Scraping plates and cooking utensils into rubbish or recycling bins before washing
• disposing of waste fats and oils (such as from the deep fryer) separately (never put this down the drain)
• using minimal fat and oil for cooking
• recycling fats and oils
• dry sweeping before hosing down floors.

Regular cleaning and maintenance are essential for maintaining your grease trap whatever type it is. Environmental Health Officers and Trade Waste Officers will visit you to make sure you are operating your grease trap properly.

Legal requirements

• Clutha District Council Water Services Bylaw 2019
• New Zealand Building Code G13 – Foul Water
• New Zealand Building Code G14 – Industrial Liquid Waste

Grease Trap Information Brochure

For more detailed information about Grease Trap requirements for food businesses/premises download our Waste, Fats and Oils Grease Trap Brochure: