TrueFlow empties and cleans grease traps and small separators for commercial kitchens across Bracknell, Berkshire and the surrounding towns, as a one-off job or to a schedule. The contents are emptied out and removed by TrueFlow Ltd as an Upper Tier registered waste carrier (registration CBDU538687), the unit is scraped clean and put back into service, and the Waste Transfer Note is signed on site. This page covers the service itself; the case for grease management in a food business is on the kitchens and restaurants page, and commercial drainage covers everything beyond the trap.
What a grease trap clean includes
A proper clean is more than emptying. On every visit the engineer:
- Empties the unit completely. Floating fat, grey water and settled solids all come out; skimming the top and leaving the sludge is how a trap ends up “serviced” yet still half full.
- Scrapes the walls, baffles and tees. Hardened grease on the chamber and fittings is removed by hand, restoring the full working volume.
- Reinstates the unit. Baffles, seals and lids go back, and the chamber is refilled with clean water so separation starts on the first sinkful.
- Checks the outlet. Water is run through to confirm it flows freely; a sluggish outlet means grease has passed the trap into the pipe beyond.
- Records the condition. Photographs before and after, a note of anything found (a cracked baffle, a missing lid, an undersized unit), and the Waste Transfer Note, handed over on site.
What the service does not cover
Two things sit outside a trap clean. The first is installation: TrueFlow services existing units; fitting or replacing one is not part of this service. The second is used cooking oil, a separate waste stream that Thames Water’s guidance for food businesses says must go to a licensed waste carrier. It should never go into a trap, and a trap clean does not dispose of it.
How often a grease trap needs servicing
Thames Water’s guidance for food businesses draws one firm line: grease recovery units (the mechanical type) need emptying every day as part of the kitchen’s cleaning routine. For passive traps and separators it says only that they must be “checked and cleaned out frequently”. The most useful yardstick is the quarter-depth rule that many North American sewer authorities write into their ordinances, explained in the FAQs below. The starting interval is set from the unit’s capacity against the kitchen’s throughput.
The paperwork, in one paragraph
The Waste Transfer Note the engineer signs on site is the written description of the load that the waste duty of care requires the kitchen to keep for two years; the carrier check is TrueFlow Ltd’s Upper Tier registration CBDU538687 on the Environment Agency’s public register. The full legal picture, including the penalties, is in the guide to grease trap regulations in the UK.
Pair the clean with jetting of the line behind it
An empty trap says nothing about the pipe beyond it. Whenever a trap runs at capacity, grease passes the outlet and cools on the walls of the run beyond, and that layer stays after the trap is cleaned. Combining the trap service with high-pressure jetting of the kitchen line (from £150 including VAT, at up to 4000psi) deals with both halves in one attendance: the trap is emptied and washed out, then the downstream run is jetted back to full bore while the engineer is on site, so the drain stays clear between services.
What grease trap cleaning costs
The price of a trap clean turns on two things: the size of the unit and how often it is serviced. A small under-sink trap is a quick job with little waste to carry away; a floor-standing or larger unit holds several times as much and takes correspondingly longer. A trap serviced before it is overdue is faster to clean than one whose contents have set solid, so a regular schedule generally costs less per visit than an overdue call. There is no single list price, then: the site visit that sets the figure costs nothing, and the exact price is agreed before any work starts.
Visits outside service hours
Trap cleans go into the kitchen’s dead time, early morning or after close for most food businesses, and a trap that fails mid-service is treated as an emergency: call-outs from £120 including VAT, with a 60-minute response target. Every visit is insured and carries a 6-month guarantee.
Grease trap cleaning FAQs
What is the 25% rule for grease traps?
A servicing threshold used by many sewer authorities, mostly in North America: floating grease plus settled solids, measured as a share of the trap’s total liquid depth, and at 25% or more the unit is pumped. UK guidance fixes no percentage, but it is a sound test of whether a trap is serviced often enough, because past that point too little volume remains for separation and grease passes through.
What is the difference between a grease trap, a grease interceptor and a GRU?
All three separate fat, oil and grease from wastewater; the difference is scale and mechanism. A grease trap is a small passive unit near the sink, relying on cooling and settling. A grease interceptor, the grease separator of BS EN 1825, works the same way at far greater capacity, usually below ground outside. A grease recovery unit (GRU) is mechanical, skimming grease into a container that Thames Water says needs emptying every day in-house.
Why does my grease trap smell?
Because the fat and food solids inside are decomposing without oxygen and giving off hydrogen sulphide, and the longer they sit the more there is. A trap that smells through its lid is usually full or close to it. One that smells shortly after a clean points to a damaged seal, a lid that no longer closes properly or a lost water seal.
Does a grease trap need refilling with water after it is cleaned?
Yes. A passive trap only separates grease while it holds water: wastewater has to slow down and cool in a full chamber for the fat to float and the solids to settle. Put back into service dry, the trap lets the first sinkfuls run straight through to the pipework beyond, so refilling the chamber with clean water is the last step of every clean, and water is then run through to confirm the level holds and the outlet is clear.
What happens if a grease trap is never emptied?
It stops working, then it causes a blockage, then it becomes a compliance problem. Once full it separates nothing: fat rides through with the water and sets in the pipework beyond until the kitchen line blocks, usually during service. Thames Water’s inspectors return to check equipment is maintained, and in 2025 a London takeaway was prosecuted after its trap, installed in 2018, was found not to have been maintained.
Book a trap clean or set up a schedule
For a one-off clean, a scheduled programme or a free site visit to size the job, call TrueFlow on 0808 175 7440 or request a site survey. The Waste Transfer Note comes with every collection.