Actionable guides and industry insights to support your food business

What is a grease trap and why does my business needs one?

It’s essential to know that if you don’t have a good grease maintenance plan, you’re putting your business’s reputation at risk. Under the Water Industry Act 1991, it is a criminal offence to discharge into the public sewers any matter which may impede the free flow of wastewater, and British Building Regulations state that commercial food premises connected to the mains drainage system and serving hot food should be fitted with a grease trap.

Water utilities currently spend around £100 million per year on clearing blockages, 75% of which are linked back to food businesses. Installing and maintaining an effective grease trap ensures that you are not contributing to this growing environmental problem, while the waste from grease traps can be collected at source and used in processes such as biodiesel generation.

With some planning, and a functioning grease trap, you’ll see how easy it is to manage your restaurant grease and comply with FOG regulations.


What is a grease trap?

Grease traps are devices that your kitchen wastewater flows through on the way to the sewer. These devices separate grease and other fatty waste from the water before it can reach the sewer.

There are different types of grease traps, but a standard trap has two chambers. As your kitchen wastewater flows through the first chamber, it captures the grease. Once it solidifies, it will float to the top of the first chamber, allowing the clean water to flow into the second chamber.


Which businesses need a grease trap?

  • Restaurants and takeaway outlets
  • Bakeries and cafes that prepare food on the premises
  • Supermarket counters that prepare food on the premises
  • Mobile food outlets
  • Schools and colleges
  • Catering companies
  • Hospital and care home kitchens

Almost any business that produces significant quantities of fats, oils, and greases needs to install a grease trap.


What type of grease trap do I need?

Installing the right grease trap is important to avoid any long-term problems. Indoor grease traps are smaller volume tanks that can be installed at different locations throughout the kitchen.

Some typical locations for indoor grease traps include:

  • Pot sinks
  • Rinse sinks
  • Food prep areas
  • Food storage areas
  • Floor drains and sinks

Outdoor grease traps on the other hand are larger and usually installed outside in the ground.


The type you choose will depend on the amount of grease and fatty waste your kitchen produces. Be sure to consider the size carefully if you are changing or installing a grease trap for the first time.


The main types of grease traps

Passive, indoor grease traps are smaller. They are usually found close to the point of use. These grease traps use a series of baffles to collect the grease and prevent it from flowing from one end of the system to another. Once the grease cools, it will accumulate at the top of the trap above the water. These traps are the most common due to their relatively low price and how easy they are to install.

Passive, outdoor grease traps are large and typically found underground. They are recommended for larger restaurants. These traps require grease waste to be pumped out by a contractor and taken away. 

Automatic grease removal units are the most expensive type of grease trap. They use a blade to automatically remove the grease into a separate container, which is cleaned out by staff daily.


How much does a grease trap cost?

Grease control devices range in cost based on type and size requirements. The cost of replacing a grease trap also depends on its current location. Many old buildings have traps located underground, requiring removal before starting any plumbing work. 

If you are installing a new grease trap and have the option, install it outside as this will make it easier to maintain and replace it in the future. 


How often do I need to clean my grease trap?

Grease traps fill up fast, so you must have a regular cleaning and maintenance schedule. As the grease trap fills up, it becomes less effective at preventing grease from getting into your pipes.

How often your grease trap needs emptying will depend on the size and the amount of grease you produce in your kitchen. A good rule of thumb for grease trap cleaning is every 1-3 months. We recommend your grease trap is pumped out by a contractor at least four times every year. 

Note that the longer you leave it between cleanings, the more chance the grease will harden and be far more challenging to remove, increasing the time required and price. Regular cleaning will keep your grease trap performing effectively and reduce the chances of costly blockages.


How long do grease traps last?

Grease traps can last up to 20 years, but this depends on your cleaning frequency. Trap damage will occur over time due to the nature of repeated cleanings. If the inside gets dented or the main wall becomes dislodged, the trap will stop functioning, requiring a change.


Grease trap warning signs

There are several ways in which your grease trap can stop functioning. Blockages of the main pipe connecting the first and second chambers are the most common. This type of backup could result in grease flowing into the sewer system, building up and causing sewer overflows. A blockage in the outgoing line will also result in a grease trap overflowing. 

If your trap becomes clogged, the first sign will be a smell of grease and oil which lingers in your kitchen. If this occurs, check your device immediately as the problem will only worsen and your customers will start to notice the foul odour.


How SwiftQuote helps

At SwiftQuote, we connect businesses like yours with approved grease service providers. You can submit a free request for service quotes from all of the suppliers in your area through the app, and set up recurring services based on your cleaning schedule. When you book a grease cleaning with SwiftQuote, we will also automatically submit job details to the local water company on your behalf.

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