Commercial Kitchen Fat, Oil and Grease Drainage Guide

Fat, oil and grease—often shortened to FOG—can cool and solidify inside kitchen drains. A blockage can stop trading, create odours, attract pests and cause wastewater to return through low-level fittings.

Understanding the system shows which observations matter and where DIY should stop. The aim is not to turn every homeowner into an engineer, but to help you describe the installation clearly and make a proportionate next decision.

How to use this information

Underground drainage is hidden, so a good diagnosis works from evidence: flow tests, inspection chambers where safe to access, the history of previous blockages and, when necessary, a CCTV survey. Clearing flow without understanding a recurring fault can leave the underlying defect untouched.

Build control into daily kitchen work

A grease trap that is too small, badly located or rarely emptied can become part of the problem. Keep service records, waste-transfer information and details of any recurring drainage symptoms. Slow flow, smells and repeated sink backups are early warnings.

A trap needs an intact water seal and a clear, correctly ventilated waste route. Refilling a dry trap may stop an occasional smell, but a recurring odour needs diagnosis.

• Scrape food into the correct waste container before washing plates and pans. Remove the material at source and put it in the appropriate bin or recycling route. Forcing unsuitable waste farther into the pipe can turn a local restriction into a deeper blockage.
• Dry-wipe greasy utensils and use sink strainers to capture small solids.
• Store used cooking oil in sealed containers for collection by an authorised contractor.
• Install an appropriately selected grease separator or removal unit where required.
• Clean and maintain FOG equipment to a documented schedule. Write down the date, location, observation and action taken. A concise record helps the next inspection distinguish a new change from an established condition.
• Train every shift and display simple instructions at preparation and wash-up points. Note which fixtures are affected and whether the result lasts. That evidence indicates whether the action addressed the cause or only moved the restriction.

How to assess your own system

1. Ask whether neighbours have symptoms too, because a shared or public sewer fault may need the sewerage company.
2. Record odours, noises, water levels and the weather conditions instead of repeatedly forcing water through the system.
3. Use only a simple, non-destructive first measure that suits the fitting, and stop if it does not improve flow promptly.
4. For recurring faults, request diagnosis such as CCTV or root-cause testing before agreeing to excavation or lining.
5. Stop using the affected fittings if water is rising, sewage is escaping or continued use could flood the property.

Common mistakes to avoid

• Assuming every pipe within the garden is privately owned without checking the drainage layout.
• Treating repeated clearing as a permanent repair when roots, displacement or collapse may be present.
• Putting hands into contaminated water or an inspection chamber without suitable controls.
• Mixing different drain chemicals or using chemicals after a product has already failed.

UK context and safety

Southern Water explains that food businesses must manage FOG so it does not block or damage the sewer network. Section 111 of the Water Industry Act 1991 prohibits discharges likely to interfere with the free flow of a public sewer. Do not rely on emulsifiers or hot water to move grease further downstream.

Wastewater can contain harmful microorganisms. Keep children and pets away, avoid direct contact, ventilate the area and wash thoroughly after any minor clean-up. Never enter a drain, sewer or confined chamber. Ownership also matters in England and Wales: the sewerage company usually maintains public sewers and many lateral drains, while the property owner is normally responsible for a drain serving only that property within its boundary.

Prevention and ongoing care

A little planned care usually provides more value than repeated emergency intervention.

• Deal with slow flow early and note whether the same branch has needed previous attention.
• Keep accessible gullies and grates free of leaves without pushing debris into the pipe.
• Use planned CCTV inspection where a property has recurring blockages, mature trees or known old clay drains.
• Retain survey footage and repair records so later contractors can compare changes accurately.

Useful UK guidance

• Ofwat: public and private sewer responsibilities

When to call PHD24

PHD24 can assess commercial kitchen drainage, clear blockages, inspect pipework and help plan grease-management maintenance. For recurring faults, ask for the underlying cause and a service schedule rather than treating each backup as an isolated event.

A useful drainage visit should do more than restore flow. The engineer should confirm the likely location, explain whether the symptom suggests a blockage or structural fault, and recommend CCTV, jetting, repair or monitoring only where the evidence supports it.

Call promptly if water cannot be isolated, wastewater is entering the property, heat or hot water has failed in vulnerable circumstances, or the fault involves gas, wet electrics or a risk to the building. For a non-urgent visit, photographs and a short history help PHD24 plan the right first attendance.