Guide
Grease traps and commercial kitchen drainage: costs and choices
Updated
Fats, oils and grease are the reason a kitchen drain blocks, and the reason water companies take an interest in your unit. Planning for them early is much cheaper than retrofitting.
Why grease management is not optional
Fats, oils and grease leaving a kitchen cool and solidify in the drainage network. That causes blockages on your premises first and in the public sewer afterwards, and water and sewerage companies expect food businesses to prevent it. Beyond the regulatory position, the practical one is simpler: a blocked drain closes a kitchen, and closing a kitchen costs more per day than any trap.
The options, and what each one commits you to
- Passive grease trap
- A chamber that separates grease by gravity, under the sink or in the floor. Lowest capital cost, highest discipline requirement: it must be emptied and cleaned on a schedule, and a neglected trap is worse than none.
- Automatic grease recovery unit
- Skims and collects grease mechanically, reducing manual emptying. Higher capital cost, needs power and access, and still needs servicing.
- External interceptor
- A larger below-ground unit serving a whole premises. Needs external space, vehicular access for tankering, and a servicing contract. Often the answer for larger kitchens and for landlords fitting out several units.
- Dosing and biological systems
- Used alongside physical separation in some installations. Treat claims carefully and ask what your local water company and environmental health team expect.
What drives the drainage cost in a fit-out
- Where the existing drainage runs, and whether it can take a kitchen's load. A survey before design is cheap insurance.
- Floor build-up. Channel drains and gullies need falls, and creating falls means building up or breaking out the floor.
- Space for the grease equipment, with access for servicing. Discovering there is nowhere to put it after the layout is fixed is expensive.
- Reinstatement: slip-resistant flooring with coved detail, laid after the drainage, is a specification item in its own right.
- Servicing access, including whether a tanker can reach an external interceptor.
- The ongoing contract, which is an operating cost you carry for the life of the business.
Getting it right
- Commission a drainage survey before the kitchen layout is finalised.
- Ask the designer to size the grease equipment against the actual menu and covers, not a generic assumption.
- Confirm with your local authority and water company what they expect for your type of premises.
- Fix the physical location and service access on the drawing before equipment is ordered.
- Get the servicing contract quoted at the same time as the installation, so the running cost is visible in the business plan.
- Keep the service records. They are the evidence that the system is being maintained.
Requirements for grease management vary between local authorities and water companies, so confirm the position for your premises rather than assuming what applied at your last site still applies here.