Dealing with FOG (Fat/Oil/Greases) in your Commercial Kitchen

Commercial kitchens process huge volumes of food, as well as perform washing, rinsing, and cleaning tasks every day, and a silent challenge runs through the drains: FOG (Fats, Oils, and Grease). If not managed correctly, FOG will clog drainage, cause foul odours, attract regulatory fines, and damage your reputation.

What is FOG in Commercial Kitchens?

FOG, in the context of commercial kitchens, refers to fat, oil, and grease. It comes primarily from cooking, frying, food residues, sauces, and cleaning processes. When warm, they flow with wastewater, but as the temperature drops, they cool, solidify, congeal, and cluster. If it goes down the sink or drains, it can build up in the pipework and slow down the flow of wastewater. Over time, this can completely block pipes. 

FOG contributes to thousands of sewer blockages (through fatbergs, large lumps of congealed FOG and waste) each year, which cost the UK nearly £200 million a year to clean. The Foodservice FOG Management Guide, published by the FEA, warns of flooding, pollution, and environmental harm if FOG is mismanaged. 

The UK has around 360,000 FSEs (Food Service Establishments), and each will produce FOG that needs treatment. However, a recent study found that only 12% of FSEs used FOG management equipment, while only around 0.15% complied with FOG management best practice. 

The Law of FOG in the UK

 

Water Industry Act 1991

Under Section 111 of the Water Industry Act 1991, no person shall permit matter, including FOG, to enter the public sewer in a way that impairs free flow or prejudicially affects its contents. In practice, this includes discharging fats, oils, or greases into drains that cause blockages or harm to sewer networks. 

 

Building Regulations & Approved Document H

The Building Regulations 2000, under Approved Document H, require that kitchens in commercial hot food premises be fitted with a grease separator that complies with BS EN 1825-1 or other effective means of grease removal. 

While the regulations don’t force one specific device, they do require “other effective means” of grease removal, meaning you must prove your FOG control system is adequate. 

 

Environmental Protection Act & Duty of Care

Under the Environmental Protection Act 1990 and the Duty of Care Regulations 1991, FOG collected from kitchens is treated as controlled waste. You must ensure proper storage, handling, and legally compliant disposal via licensed waste carriers. 

 

Food Hygiene & Local Authority Inspections

Under the Food Safety Act 1990 and associated Hygiene Regulations, a kitchen must prevent grease build-up and maintain cleanliness to avoid contamination risks. Local authorities inspect commercial kitchens, and a failure to manage FOG may be flagged as a hygiene or drainage issue. 

Equipment & System Solutions to Manage FOG

To stay compliant and prevent damage, kitchens should deploy appropriate equipment systems, ideally in conjunction with good operational practices. 

 

Grease Separators / Grease Traps

The most traditional solution is a grease separator or trap installed in the wastewater line, where FOG is allowed to separate before water passes into drains. Grease, being less dense, floats to the top; heavier solids sink, and clearer water exits the trap via a lower outlet baffle. 

These traps must be sized and installed according to flow rates, sink and dishwasher connections, and conform to BS EN 1825-1 standards.

 

Grease Removal Units (GRUs) & Automatic Traps

GRUs are more advanced devices that automatically collect and skim FOG into separate chambers or disposable cartridges. Some are mechanical (automated) or manual, but they reduce the burden on kitchen staff compared to passive traps. 

They often require less frequent manual intervention, but still need servicing, emptying, and maintenance to remain effective.

 

Biological / Dosing Systems

Bio-dosing systems inject beneficial bacteria or enzymatic solutions into drains to degrade FOG in situ. These systems can be used in conjunction with separators or traps to minimise accumulation downstream. However, they must be carefully selected (not just emulsifiers) because some additives can cause further issues along the drain system. 

 

Integrated Grease Management Systems & Smart Solutions

Some manufacturers, like ACO, offer high-performance grease management systems (e.g. LipuSmart) equipped with sensors, automated pumping, and level detection to manage grease behaviour proactively. 

Such systems can help reduce manual intervention, alerts, and overflows, and provide better control in larger operations. 

What to do with Collected FOG

 

Storage & Containment

•    Use dedicated, sealed containers (metal or approved plastic) for FOG, labelled clearly.
•    Store the containers in a well-ventilated, secure area away from food preparation areas.
•    Keep a log of volume, storage times, and condition.

 

Licensed Waste Carriers & Waste Transfer Notes

You must contact an Environment Agency-licensed waste carrier to collect and dispose of FOG and receive a waste transfer note for each collection as proof. This is part of your legal duty of care. 

 

Recycling & Reuse Options

In some regions, collected FOG (especially used cooking oil) can be processed for biodiesel or industrial use, provided it is properly segregated and handled. However, FOG from dishwashing with food residues may not always be suitable. Always check local regulations for recycling or biofuel use.

 

Frequency of Removal

Depending on the volume, some kitchens should empty or pump their traps weekly, while others should do so fortnightly. Overfilling or delay reduces effectiveness, allows FOG to pass through, and may lead to blockages or fines. 

 

Documentation & Audit Trails

Keep records of cleaning, servicing, volume removed, dates, personnel involved, and waste transfer notes. In the event of inspections by environmental or municipal authorities, these documents demonstrate that you acted responsibly. 

 

How Dishwashers Direct Supports FOG Management in Your Kitchen

As a leading UK commercial dishwasher supplier, Dishwashers Direct can help beyond just machines:

•    Advice on Sink and Drainage Layout: We can optimise your plumbing design to ensure FOG removal systems integrate well with dishwashing lines. 
•    Recommended Accessories and Fittings: From stainless steel grease traps to compatible fittings, we can supply components that suit your kitchen scale. 
•    Support for Compliance: Our team can guide you through tubing layouts, separator sizing, collection regime setups, and documentation best practices. 
•    Maintenance Reminders & Training Support: We help your staff understand protocols, such as scraping, dry wiping before rinsing, and grease trap cleaning schedules.
•    Compatibility with Dishwasher Waste Lines: Ensuring your commercial dishwasher doesn’t overwhelm your FOG systems through high flow or temperature surges. 

 

Practical Tips & Best Practices

•    Always scrape plates, trays, and pans to remove fat residues before rinsing or loading them into dishwashers.
•    Use plug-hole strainers to catch food solids before they reach the grease system.
•    Use hot water flushes cautiously; excessive heat can liquify FOG further down the system, prematurely bypassing traps.
•    Don’t use strong emulsifiers unless approved for your system; they may push FOG downstream.
•    Train staff to monitor trap levels, odours, or slow drainage as warning signs.
•    Schedule regular trap cleaning and service.

 

 

FOG is one of the biggest hidden threats to commercial kitchen drainage health, but with the right approach, it’s fully manageable. 

By installing and maintaining grease separators, GRUs, bio-dosing systems, or integrated smart systems and by handling collected FOG responsibly, you protect your plumbing, preserve hygienic conditions, avoid fines, and keep operations uninterrupted.

At Dishwashers Direct, we not only supply high-performance dishwashing machines but also partner with you to ensure your kitchen’s drainage and FOG systems work seamlessly. 

If you’d like help designing, sizing, specifying or servicing a FOG management system for your facility, get in touch. We’re here to ensure your drains stay clear and compliant without disrupting service.