Trade effluent explained: consents, charges and staying compliant
If your business discharges anything into the sewer beyond ordinary toilet, kitchen-sink and hand-basin wastewater, you are probably producing trade effluent — and trade effluent is regulated, consented and charged quite differently from ordinary sewerage. It is also one of the least-reviewed costs in British business. Plenty of premises pay trade effluent charges set years ago, on assumptions nobody has revisited since.
What counts as trade effluent?
Trade effluent is any liquid waste produced in the course of trade or industry that is discharged to the public sewer. Common examples:
- Washdown water from food and drink production or commercial kitchens operating at scale
- Process water from manufacturing, printing, or metal finishing
- Commercial laundry and vehicle-wash discharge
- Cooling water and boiler blowdown
What does not count: domestic-strength sewage from staff toilets and ordinary sinks. The line is about the nature and strength of the discharge, not the size of the business.
The consent: your permission to discharge
Discharging trade effluent to a public sewer without a trade effluent consent is a criminal offence under the Water Industry Act 1991. The consent is issued for your specific premises and discharge, and typically specifies:
- What you may discharge and from which process
- Maximum daily volume and flow rate
- Limits on strength and composition — chemical oxygen demand, suspended solids, pH, temperature, fats and oils, and any substances of particular concern
In England the consent is administered through the wholesaler (with your retailer often the first point of contact); in Scotland, through the Scottish framework. If you are starting or changing a process that will discharge to sewer, apply before you discharge — retrofitting compliance after an unconsented discharge is a far worse conversation.
How trade effluent is charged
Charges are commonly calculated using a cost formula — the long-established Mogden formula — which builds your charge from components reflecting what your effluent actually costs to move and treat:
- Volume — how much you discharge (measured or assessed)
- Conveyance and reception — getting it to and into the works
- Biological treatment — driven by the strength (COD) of your effluent relative to average sewage
- Sludge treatment — driven by the suspended solids you send
The practical consequence: stronger and dirtier costs more. Two businesses discharging identical volumes can face very different charges because one sends weak, cool, clean washwater and the other sends hot, fatty, solids-laden effluent.
Reducing trade effluent costs without cutting corners
Because the charge is built from volume and strength, both are levers:
- Challenge the assessed volumes. If your charge assumes a fixed proportion of incoming water is discharged, meter the actual discharge or claim allowances for water that never reaches the sewer (in product, evaporated, irrigated).
- Reduce strength at source. Dry-wiping equipment before washdown, fitting fat and grease management, screening solids, and fixing dosing errors all reduce the strength components of the formula — and they compound every single day.
- Review the sample data. Charges rest on measured strengths from sampling. If your process has changed since the samples were taken, ask for resampling.
- Compare retailers. In the open England and Scotland market, trade effluent is part of the competitive retail offer. Service quality on consents, sampling and billing varies between retailers.
Who should be thinking about this?
Trade effluent is not just a heavy-industry topic. Takeaways, restaurants and food producers washing down equipment at scale; laundrettes and commercial laundries; car washes and valeting operations; breweries and microbreweries; and workshops using degreasers or coolants can all fall within it. A useful rule of thumb: if what goes down your drains is noticeably different from what goes down the drain of an ordinary office — hotter, fattier, stronger, more chemical — the question is worth asking formally. Plenty of small operations discharge trade effluent for years without a consent simply because nobody ever told them the category existed; discovering it during an inspection is the worst way to find out.
Moving premises or changing hands? The consent does not follow you
A trade effluent consent belongs to a specific occupier discharging from specific premises. Take over a site — even one that has discharged the same effluent for decades — and the previous occupier's consent does not automatically become yours; the incoming business needs its own application in place before discharging. The same logic applies to changes in what you do: a new production line, a change of process chemicals or a step-change in volume can take your discharge outside the terms of the existing consent, and the time to raise it is before the change goes live.
Compliance is not optional
Breaching consent conditions — or discharging without one — risks prosecution, and the operational fixes demanded afterwards are rarely cheaper than doing it properly first. Keep your consent document accessible, know your limits, and if production is changing, talk to the wholesaler before the discharge changes, not after a sample fails.
Getting help with the whole picture
We review trade effluent alongside water supply and sewerage as one cost picture: consents, charges, allowances and the retail market together. The review costs your business nothing — if you switch retailer through us, the retailer pays our commission, disclosed in full on this site. Use the quote form on our homepage and a UK-based water specialist will call you back.
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