Grease traps and fats, oils and grease (FOG) management in commercial kitchens.
Commercial kitchens generate fats, oils and grease every day. Keeping FOG and food waste out of drains protects the sewer system and helps prevent blockages, sewage backflow and hygiene incidents. This guide covers grease traps, sink strainers, used cooking oil, maintenance, drainage failures and practical records.
Practical guidance from TKEG (The Kitchen Efficiency Group), built around everyday UK hospitality compliance and kitchen operations.
Why do commercial kitchens need to control fats, oils and grease?
Fats, oils and grease (FOG) are produced during cooking, food preparation and washing up. If they enter sinks and drains they can cool, solidify and combine with food debris, restricting pipes and contributing to sewer blockages, flooding, odours and pollution.
For a food business this is not only a drainage issue. A backed-up drain or sewage incident can contaminate food areas, disrupt service and create a serious hygiene problem that may require the affected area to stop operating until it is safely restored.
Should cooking oil or fat ever be poured down the sink?
No. Waste cooking oil, liquid fat and greasy residues should be kept out of sinks and drains. Scrape food into the appropriate waste container and dry-wipe heavily soiled pans, trays and utensils before washing where practical.
Use suitable sink strainers to catch food particles that would otherwise enter the drainage system. Hot water should not be relied on as a way of sending fat safely through the drain: grease can simply cool and solidify further along the pipework.
Does every commercial kitchen legally need a grease trap?
The correct grease-management arrangement depends on the premises, drainage system, activity and the requirements of the relevant water or sewerage provider. Government guidance for food businesses recommends grease-management equipment such as grease traps or grease-removal units to prevent residual FOG entering drains.
Avoid treating one particular grease-trap design or size as a universal legal requirement. A higher-volume restaurant, hotel or production kitchen may need a different solution from a small low-grease operation. Specialist assessment and the requirements of the sewerage provider may determine the appropriate equipment.
What does a grease trap or grease separator do?
A grease trap or separator slows wastewater so that lighter fats, oils and grease can separate from the water instead of continuing directly into the drainage system. Grease-removal units use different designs but have the same broad objective: reduce the amount of FOG reaching the sewer.
The equipment only works if it is appropriately sized, installed and maintained. An overloaded, damaged or neglected unit can allow grease to bypass the system and can itself become a source of odour, pests or hygiene problems.
How often should a grease trap be emptied and cleaned?
There is no single servicing interval that fits every commercial kitchen. Frequency should reflect the equipment specification, kitchen output, grease load and actual condition of the unit. Follow the manufacturer or specialist service recommendations and increase attention if grease is building up too quickly, drainage slows or odours develop.
Management should be able to show that the unit is being maintained often enough to remain effective. A fixed calendar tick is less useful than evidence that the trap is checked, cleaned and serviced according to the real operating load.
What should happen to used cooking oil?
Store used cooking oil in a suitable secure container rather than pouring it into sinks, floor drains or outside gullies. Prevent spills and make sure the container is positioned where it will not contaminate food, block access routes or attract pests.
Where a specialist waste contractor collects used oil, include the collection within the business waste-management and duty-of-care records. Follow the requirements that apply to the waste stream and local collection arrangement.
What if a drain is slow, blocked or backing up?
Treat recurring slow drainage as a warning rather than waiting for a full blockage. Stop practices that may be adding FOG, check accessible strainers and grease-management equipment, and arrange competent drainage or maintenance support where required.
If wastewater or sewage backs up into a food area, protect exposed food and food-contact equipment immediately and assess whether the affected area can continue operating safely. Cleaning, disinfection, disposal of contaminated food and corrective action may be needed before reopening the area.
What records are useful for grease management?
Useful records can include grease-trap inspections, emptying or servicing, contractor visits, used-oil collections, recurring drainage problems and corrective actions. Keep enough information to show what happened and what action was taken without creating unnecessary paperwork.
Grease-management records fit naturally alongside cleaning, maintenance, waste and opening/closing checks because failures often cross more than one part of the kitchen operation.
A practical FOG-control routine for kitchens
Scrape plates and pans before washing; dry-wipe greasy equipment where practical; use sink strainers; keep cooking oil out of sinks and drains; operate suitable grease-management equipment where required; store waste oil securely; inspect drainage warning signs; maintain equipment; and record meaningful failures and corrective action.
Managers should also train staff on why these controls matter. A correctly installed grease trap will not compensate for staff routinely pouring fryer oil, sauces or food debris into the drainage system.
Practical guidance, checked against official UK sources.
TKEG guidance is written for practical hospitality use. Where a topic involves regulation, official schemes or workplace safety, businesses should also consult the current guidance from the relevant authority and apply it to their own operation.
TKEG is independent and is not affiliated with or endorsed by the Food Standards Agency, HSE or a local authority. Official guidance and legal requirements take precedence where applicable.
Put the guidance through a practical check
Use our free interactive tools to assess inspection readiness, generate a tailored checklist, check temperatures, review training needs, test allergen and COSHH controls, or review your HACCP-based food-safety management system.
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Move between the core topic hubs to understand how food-safety records and controls connect.
Continue with closely related guidance
Commercial kitchen waste management
Read the TKEG guide.
Commercial kitchen cleaning schedules
Read the TKEG guide.
Commercial kitchen maintenance
Read the TKEG guide.
Power cuts, water outages & kitchen emergencies
Read the TKEG guide.
Pest control in commercial kitchens
Read the TKEG guide.
Food safety corrective actions
Read the TKEG guide.
Related TKEG software and workflows
TKEG helps hospitality teams record, manage and evidence many of the day-to-day controls covered in our guides.
Common questions
Does every restaurant need a grease trap?
There is not one universal grease-trap specification for every restaurant. The appropriate arrangement depends on the business, drainage system, grease load and relevant sewerage-provider requirements, but government guidance recommends grease-management equipment to keep residual FOG out of drains.
Can I pour cooking oil down the sink with hot water?
No. Hot water does not make waste oil or grease suitable for drain disposal. The grease can cool and solidify further along the drainage system.
How often should a grease trap be cleaned?
There is no single interval for every kitchen. Follow the equipment and service guidance and clean or service it often enough to remain effective for the actual grease load.
Should food waste go down a commercial kitchen sink?
No. Scrape food waste into the appropriate waste container and use sink strainers to reduce food particles entering the drain.
What should a restaurant do if sewage backs up into the kitchen?
Protect food and food-contact equipment, stop using affected areas where safe operation cannot be maintained, arrange repair and cleaning, dispose of contaminated food where necessary and document the corrective action.
Turn the paperwork into a working system.
TKEG brings food-safety records, compliance evidence and kitchen management together.