Guide
Grease trap regulations UK: what the law actually requires of kitchens
Updated
There's no single "grease trap law", but three strands add up to the same practical duty: a commercial kitchen needs adequate grease separation, kept working. Here's each strand in plain terms.
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The sewer offence: Water Industry Act 1991, Section 111
Under Section 111 of the Water Industry Act 1991, it is an offence to discharge into public sewers any matter likely to interfere with the free flow of their contents. This is the provision water companies rely on over fat, oil and grease: congealed grease is a leading cause of sewer blockages, and where a blockage traces back to a kitchen, the water company can pursue the business for the offence and for clearance costs. A working, serviced grease trap is the practical defence: it keeps the grease out of the sewer in the first place.
The building side: Part H and BS EN 1825
Building Regulations Approved Document H (drainage and waste disposal, gov.uk) expects commercial hot food premises to have means of grease separation on kitchen drainage, and points to the British Standard for grease separators, BS EN 1825, which covers how separators are sized (from flow rate and use) and how they are installed, operated and maintained. In practice: new builds and kitchen fit-outs get a trap or separator sized to the standard at build time, and an existing kitchen without one has a gap that both building control and the water company can call out.
The waste side: what leaves the trap
- Grease trap waste is controlled waste: it must be removed by a registered waste carrier and you should receive and keep a waste transfer note for each collection, that paper trail is your duty-of-care evidence.
- Used cooking oil is collected separately: it goes in dedicated containers for collection, never down any drain, trap or not.
- Environmental health looks at the whole picture: food hygiene inspections take in drainage and grease management, and a smelly, overflowing trap is a finding, not just a plumbing problem.
What compliance looks like day to day
- Have adequate separation: a trap or separator sized for the kitchen's flow, per BS EN 1825 for new installations; if you don't know what you have, get it surveyed.
- Service it on a schedule that matches throughput, commonly every 1–3 months for busy kitchens, see the interval guide.
- Keep the records: service dates, volumes and waste transfer notes in one folder. When a water company inspector or EHO asks, that folder is the answer. Get quotes from firms that handle the servicing and the paperwork together.