Trade Effluent


Trade effluent is anything other than domestic sewage. If you want 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 or activity. This can be best described as anything other than domestic sewage (toilet, bath, sink or kitchen wastewater 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 who need very small discharge volumes, occasional discharge or a one-off event and when the effluent is proven to be of very low risk for the sewer and receiving wastewater treatment 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:

  • 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 suite of metals. Other analytes may be relevant to your business activity such as anionic detergents, sulphate, methane and cyanide. Please include further details as appropriate.
  • Provide drainage plans as we may need to assess and inspect your drainage plans to avoid unconsented discharges (and surface water entering our network) where not consented, to reduce the volume entering our sewers.
  • How is the flow discharge going to be monitored in terms of metering.
  • Provide detail on the intended volume of discharge in meters cube per day and maximum instantaneous 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 send back 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. We may not be able to accept effluent containing certain substances.

Please contact us if you would like to discuss further. Our assessments are all carried out on a case-by-case basis and we cannot guarantee that there is capacity for your 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. In some cases, we may be unable to treat your effluent and cannot issue a consent. We will provide you with details of the reasons for the refusal of the consent.

Do we keep a record of our Trade Effluent discharge consents?

It is a legal requirement for us to keep a register of all trade effluent consents we issue, which are available to the public on request. These are held in a trade effluent database register.

Please email us at Trade.Effluent@dwrcymru.com if you would like a copy of a consent held in the register or a copy of the public register.

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.

How are trade consents monitored?

Our trade effluent team may sample your effluent at a varying frequency based on the composition of your discharge and how often you are billed. Sample results are compared to your consent limits to ensure results are within agreed conditions.

What if you breach your consent?

Breaches of consent conditions will be communicated to you with a formal letter, asking you to investigate further and report your findings to us. We will ask you for information such as the root cause of the breach, the steps taken to restore your discharge quality and details of long-term actions for improvements.

Our Enforcement Policy sets out the staged process that we will follow when there are breaches of the consent conditions.

Legal action will be taken against persistent non-compliance and discharges with an adverse impact on the integrity of our assets and/or public health and safety, and/or the environment.

We reserve the right to recover any cost incurred following a breach.

Frequently asked questions about trade effluent

Still need more information?

If you still have unanswered questions, please email our trade effluent team on Trade.Effluent@dwrcymru.com