Trade Effluent

Trade effluent is anything other than domestic sewage. If you need to discharge trade effluent into one of our public sewers, you need our permission.

What is trade effluent?

Trade effluent is any liquid waste (effluent) discharged into our sewers from a business or industrial process. This can be best described as anything other than domestic sewage (toilet, bath or sink waste) or uncontaminated surface water and roof drainage (rainwater).

Do businesses need permission to discharge trade effluent?

Yes. It is a legal requirement for any business to get our permission before any discharge to our public sewers takes place, under the Water Industry Act 1991. This is because illegal discharges can have severe effects on the environment, damage our sewers, inhibit our wastewater treatment processes, and pose a significant health and safety risk to our employees.

What kinds of permission are there?

We can issue two different forms of permission:

  • A trade effluent consent with prescribed maximum limits for several parameters including flow which are subject to regular monitoring by our trade effluent inspectors; or
  • A letter of authorisation for those businesses who need very small discharge volumes, occasional discharge or a one-off event and when the effluent is proven be of very low risk for the sewer and receiving sewage works.

A trade effluent consent or letter of authorisation is a legal agreement between us and your business stating the permitted limits of discharge strength and volume.

My business needs to discharge trade effluent. How do I get your permission?

You can request permission by completing our trade effluent enquiry form. Before you proceed you may need to gather the following information:

  • Compile any sample data information you may have with analysis for at least biological oxygen demand, chemical oxygen demand, settled chemical oxygen demand, suspended solids, ammonia (measured as NH4-N), total phosphorus (measured as PO4-P), fats oils and greases, pH and a suit of metals. Other analytes may be relevant to your business activity such as anionic detergents, sulphate, methane and cyanide.
  • Drainage plans as we may need to assess and inspect your drainage plans.
  • How is the flow discharge going to be monitored in terms of metering.
  • Intended volume of discharge in meters cube per day and maximum instant flow.

What happens after I submit my enquiry form?

After processing your enquiry, we will send you a document called a ‘preliminary details form’ for you to complete and email (or post) to us, along with other supporting information.

Once we’ve received your preliminary details form, we will assess the acceptability of the discharge to the receiving sewer, pumping stations and wastewater treatment works.

For businesses handling very toxic chemicals such as chromium, lead, zinc, cadmium and cyanide amongst others we are required to carry out a more comprehensive environmental risk assessment so our determination may take longer.

This is all done on a case-by-case basis and we cannot guarantee that there is capacity for your business’s effluent however we may be able to offer a lower discharge volume and strength.

If the risk of accepting a discharge is acceptable, we will issue you with a formal notice or application. You must return this fully signed and dated, so that we can issue you with formal ‘Consent to Discharge’ documentation that will allow you to discharge.

What costs are involved when it comes to requesting trade effluent permission and when do I need to pay them?

There are no upfront charges and you will only be charged if a consent is granted. The fee is detailed in our scheme of charges and reviewed annually.

Frequently asked questions about trade effluent

Still need more information?

If you still have unanswered questions, email our trade effluent team on