A trade effluent consent is the formal permission you need to discharge industrial or commercial liquid waste into the public foul sewer. It is granted by your water and sewerage company (the sewerage undertaker) under the Water Industry Act 1991, and it sets the volume, strength and conditions under which your discharge is allowed.
What is a trade effluent consent?
A trade effluent consent is a legal document, issued by the sewerage undertaker for your area, that authorises you to discharge trade effluent into the public sewer and sets the conditions you must meet. Trade effluent is, broadly, any liquid waste from a business or industrial process — it excludes ordinary domestic sewage and uncontaminated surface water. If your premises produce process water, washdown, cooling water or similar that goes to the foul sewer, you almost certainly need a consent.
The legal basis is the Water Industry Act 1991, which makes it an offence to discharge trade effluent to a public sewer without consent. The consent protects three things: the sewer network itself, the biological treatment process at the water company works, and the environment into which the works ultimately discharges. Because the water company carries the cost and risk of treating what you send, it has a statutory right to control the volume and quality of your discharge through the consent.
It is worth being clear about what counts as trade effluent, because the boundary catches more businesses than people expect. The term covers liquid waste from any trade or industrial activity discharged to the public foul sewer, from manufacturing and food production to vehicle washing, laundries, laboratories and many commercial kitchens. It does not cover ordinary domestic sewage from toilets and staff welfare, nor clean surface water and roof drainage, which follow separate routes. If you are unsure whether your discharge qualifies, the safe course is to ask the water company rather than assume it does not.
Who grants it, and how does that differ from an environmental permit?
A trade effluent consent is granted by your water and sewerage company, not by an environmental regulator. This is the point most often confused. If your effluent goes to the public sewer, you deal with the water company. If it goes to a watercourse or the ground, you instead need an environmental permit from the Environment Agency (England), Natural Resources Wales, SEPA (Scotland) or NIEA (Northern Ireland).
The distinction matters because the two instruments come from different bodies under different laws, with different application routes and different enforcement powers. A common and costly error is applying to the Environment Agency for a discharge that actually goes to sewer, or assuming a single permission covers both routes. Confirm your discharge point first; everything else follows from it. Specialists who provide trade effluent and discharge compliance support can confirm which regime applies to your site.
How do you apply for a trade effluent consent?
You apply to the sewerage undertaker by serving a trade effluent notice — historically known in many companies as a Form G — at least two months before you intend to begin discharging. The notice tells the company what you propose to discharge so it can decide whether to grant consent and on what conditions. The two-month notice period is a statutory minimum that gives the company time to assess the impact on its sewer and works.
A typical application asks you to describe:
- The process generating the effluent and the materials used.
- The maximum daily volume and the peak rate of discharge.
- The composition of the effluent — its strength and the substances it contains.
- The discharge point and the proposed sampling arrangements.
The company may grant the consent with conditions, grant it subject to pre-treatment being installed, or refuse it if the discharge cannot be accommodated. You have rights of appeal if you disagree with the conditions imposed. Where the effluent contains certain prescribed (special category) substances, an additional layer of review applies before consent can be given.
What conditions does a trade effluent consent contain?
A consent sets out the envelope within which you may discharge. The conditions protect the sewer, the treatment works and, ultimately, the environment, and breaching any of them puts you outside your consent. While the exact figures are specific to your site, the parameters controlled are broadly consistent across the industry.
| Condition | What it controls |
|---|---|
| Maximum daily volume | The total quantity you may discharge in a day |
| Maximum rate of flow | The peak instantaneous discharge rate, to avoid surcharging the sewer |
| pH range | Acidity/alkalinity limits to protect pipework, concrete and biology |
| COD (and often BOD) | The organic strength the works must treat |
| Settleable / suspended solids | Solids load, to limit siltation and treatment burden |
| Fats, oils and greases (FOG) | To prevent blockages and fatbergs in the sewer |
| Temperature | An upper limit, commonly around 43°C, to protect assets and biology |
| Prohibited / restricted substances | Metals, sulphate, specific pollutants relevant to your process |
| Sampling & access | A safe, accessible sampling point and agreed monitoring arrangements |
If your raw effluent cannot meet these conditions, the answer is pre-treatment on site — for example flotation or grease management for FOG, balancing for flow and pH correction, or solids removal — so the discharge sits comfortably inside the consent before it leaves your boundary.
How is trade effluent charged?
You pay the water company for receiving and treating your trade effluent, and the charge reflects both how much you discharge and how strong it is. Most UK water companies base trade effluent charges on a formula derived from the long-established Mogden formula, which builds the charge from the cost of conveying the effluent, treating its volume, treating its organic load and disposing of the resulting sludge.
In Mogden-style charging, the bill rises with three things: the volume you discharge, the chemical oxygen demand (COD) or settled organic strength, and the suspended solids load. The stronger and more voluminous your effluent, the more you pay. This gives a direct financial incentive to reduce volume and load at source: cutting COD and solids through pre-treatment or process change lowers the ongoing charge as well as easing compliance. The precise rates and the exact form of the formula vary between companies and are published in their annual charges schemes.
What happens if you breach your consent?
Discharging outside your consent — exceeding a limit, discharging a prohibited substance, or discharging without consent at all — is a serious matter. The sewerage undertaker has statutory powers, and breaches are an offence under the Water Industry Act 1991. The likely consequences escalate with the severity and persistence of the breach.
- Investigation and warning for a first or minor breach, with a requirement to put it right.
- Increased charges or recovery of costs where the breach has imposed extra treatment or damage costs on the company.
- Variation of the consent to impose tighter conditions or additional monitoring.
- Prosecution for significant or repeated breaches, which can result in substantial fines.
- Suspension or revocation of the consent in the most serious cases, stopping your discharge entirely.
The practical safeguard against all of this is to design and operate treatment with margin, so your normal discharge sits well within consent and an upset does not immediately become a breach. Reliable pre-treatment, balancing and monitoring turn a consent from a risk into routine compliance.
Frequently asked questions
Do I need a trade effluent consent?
If your business discharges any liquid waste from a process — other than domestic sewage or clean surface water — into the public foul sewer, you almost certainly need a trade effluent consent. Discharging trade effluent to the public sewer without consent is an offence under the Water Industry Act 1991, so check with your water company before you begin.
Who issues a trade effluent consent?
Your local water and sewerage company (the sewerage undertaker) issues the consent under the Water Industry Act 1991. It is not issued by the Environment Agency, which instead regulates discharges to controlled waters. If your discharge goes to the sewer, the water company is the body you deal with for both the consent and the charges.
How long does it take to get a trade effluent consent?
You must give the water company at least two months' notice by serving a trade effluent notice (often called a Form G) before you start discharging. The company uses that period to assess the impact and set conditions. Complex discharges, or those containing special category substances, can take longer to determine.
How are trade effluent charges calculated?
Most UK water companies use a formula based on the Mogden formula, which combines the cost of conveying and treating the effluent's volume and organic load and disposing of the resulting sludge. Charges rise with volume, chemical oxygen demand and suspended solids, so reducing strength and volume at source lowers your bill.
What is the difference between a trade effluent consent and an environmental permit?
A trade effluent consent, granted by your water company under the Water Industry Act 1991, allows discharge to the public sewer. An environmental permit, granted by the Environment Agency, Natural Resources Wales, SEPA or NIEA, allows discharge to a watercourse or the ground. Which you need depends solely on where your effluent goes.