Fats, Oils and Grease (FOG) are found in kitchen wastewater. It is found in kitchen wastewater after the production of food and also washing up of food equipment, utensils and crockery.

Grease management is a term that describes a method used (such as a grease trap) to stop or remove grease before it enters the main drainage system. Commercial kitchens often have a higher amount of FOG in their wastewater effluent than domestic kitchens and it therefore needs to be managed. If neglected, solidified FOG causes blockages in the pipes that can cause sewage overflows which are costly and a public health risk. Furthermore, it is also flouting the Water Industry Act of 1991.

A grease trap is a device that captures/intercepts grease to stop it from entering the sewer system and causing blockages in the pipes. Wastewater from the kitchen enters the grease trap, due to the fact that grease is less dense, it rises to the top and floats on the surface. When the layer of grease gets deep enough, it needs to be emptied, either manually or by a trained engineer.

There are other types of grease management systems that you may find more suitable. These are:

1. Grease Removal Units (GRU) – These are similar to grease traps, but additionally capture and remove the grease into external containers for separate disposal.
2. Biological dosing systems – These units inject a combination of enzymes and bacteria into the drainage system that act to break down FOG into less harmful products.

For existing premises the reasons for fitting a FOG management system tend to be as a result of drain problems, pressure from the local water company, landlord or environmental health officer. It is however a requirement under the Water Industry Act 1991 to ensure that your premises does not discharge any product into the drain which may interfere with its operation.

Taken from the Water Industry Act 1991

Provisions protecting sewerage system 
111 Restrictions on use of public sewers 

(1) Subject to the provisions of Chapter III of this Part, no person shall throw, empty or turn, or suffer or permit to be thrown or emptied or to pass, into any public sewer, or into any drain or sewer communicating with a public sewer- 
(a) any matter likely to injure the sewer or drain, to interfere with the free flow of its contents or to affect prejudicially the treatment and disposal of its contents. Thames Water reported that in 2007/2008 over 60,500 sewer blockages reported were caused in part by FOG.

Overflowing sewers release bacteria, viruses and other pathogens that may be hazardous to human health. The sewage may be released into your business or home, or into our waterways, streets and parks. SSOs are unpleasant and expensive to clean up, and if they occur on your property, it is you, the property owner, who may be responsible for the clean-up.

Having an SSO occur in your establishment may also lower the number of customers.

If the County is responsible for a clean-up, manpower and money are wasted on something that could have been avoided. The costs associated with SSOs can include containment, removal, and disposal of contaminated materials, emergency line cleaning, disinfectants, sampling and testing, record keeping and documentation, public notification, and EPA & MCWS enforcement actions. The non-direct costs may include media related costs, property damages, public relations, insurance, worker and public exposure to untreated wastewater (pathogens and viruses) and decreased tourism. These costs will, most likely, trickle down into customers' sewer bills.

Brown grease consists of floatable fats, oils, greases and settled solids that are recovered from grease management systems. Brown grease is contaminated with food solids and is therefore difficult to reuse. Brown grease is usually disposed at a wastewater treatment facility but may become part of renewable energy sources in the future.

Yellow grease means fats, oils, and greases that have not been in contact or contaminated with other sources (water, wastewater, solid waste, etc). An example of yellow grease is fryer oil, which can be recycled into products such as animal feed, cosmetics and alternative fuel. Yellow grease is also referred to as renderable FOG.

Detergents that claim to dissolve grease are highly likely to simply facilitate the movement of grease down the pipeline and cause problems elsewhere. In short, you remove it from your immediate vicinity only to help create a larger problem downstream, which will ultimately cause you greater issues at a later date.

Additives are generally prohibited, as many tend to pass grease down the pipeline and cause additional problems in the sewage network.

If you are using deep fryers in your establishment, contact a rendering company to provide a bin or barrel for regular collection. There is also value in the re-use of oil.

The equipment listed in BS EN1825 (the British Standard for Grease Separators) includes:

• Pre-Rinse Sinks
• Pot Wash Sinks
• Dishwashers
• Tilting Roasting-tin
• Fixed Roasting-tin
• High Pressure Cleaners
• Scrapers
• Vegetable Washer

Using our grease trap sizing calculator, we can determine the correct size by two methods. The size of the kitchen and type of equipment required.

Grease traps are now a legal requirement for any business that deals with hot food. The laws were enforced by Parliament, which meant all commercial kitchens now have a duty of care and legal obligation to manage and remove FOG (fats, oil, and grease). For more in-depth information check out our ‘Are Grease Traps Required by Law’ blog.

Grease traps are made to remove FOG (fats, oil, and grease). As grease has a lower density than water, it is unable to mix with water which makes it rise to the surface. This happens because of a system of baffles. A baffle is a wall inside the grease trap, which slows down and controls the flow of water. The grease then fills the trap from the top down and the grease-free water leaves under the final baffle wall to the main sewer drain.

Grease traps should be cleaned every one to three months. However, we at Aqua Mundus provide a range of maintenance options which includes frequent maintenance, which eliminates the need for potential kitchen downtime.

Grease traps that are located below the ground surface are generally larger in size ranging from 150 litres through to 10,000 Litres in capacity. Grease interceptors up to 1,000 litres can be emptied using a mobile vacuum tank, whilst larger in ground grease traps use a vacuum tanker lorry to empty and dispose of the waste.

Under sink grease traps can be either passive manual units up to approximately 150 litres in capacity, or an automatic Grease Removal Unit (GRU) sized by litres per second flow rate. Both types of grease trap should be emptied on a maintenance programme using mobile vacuum unit with the addition of a mechanical and electrical testing service on GRU’s.

The installation process of grease traps should always be done by a specialist, like ourselves. We offer nationwide coverage for grease trap installations. Our team of engineers are fully trained, with a wealth of knowledge.

Yes. Any commercial property that serves hot food is required to own a grease trap. This law was enforced by the House of Commons in the British Building Regulation Act, Document H, Section 2.21.

The grease trap sizing calculator evaluates the price depending on the size of the kitchen and the equipment inside. However, drainage runs and invert levels also have an impact of product suitability and location, therefore a Free Site Survey is always recommended.