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Storm overflows, as well as containing a mix of rainwater and dilute sewage, contain visible litter which is flushed down the sewer or put into drains. Screens can be installed on the overflows to reduce the amount of litter that can make its way to the watercourse. These screens are usually either a row of bars or a plate with perforations in where the material that settles on them is mechanically cleaned off to remove the rag from the flow of discharge. In addition to this, Water Companies, along with Welsh Government, NRW and CCWater will continue to promote campaigns to educate customer on what should and should not be put into the sewerage system.

The level of screening that is installed at each storm overflow is defined within the Water Companies Environmental Permit. This is determined by NRW in the document ‘How to comply with your environmental permit: Additional guidance for: Water Discharge and Groundwater (from point source) Activity Permits EPR 7.01’. Water Discharge and Groundwater (from point source) Activity Permits (EPR 7.01) (  This looks at the amenity of the waterbody (how it is used) and the number of times the storm overflow is modelled/actually discharges and assesses the type of method that is suitable for limiting the discharge of solids matter, such as wet wipes, rags and large objects. This guidance is currently being revised by NRW to consider changes in modern design standards and river use.

Unfortunately, a lot of permits were set before the guidance was in place. Therefore, Water Companies need to undertake a programme of assessment against the new guidance to understand where screening is not currently in place and needs to be or, where it is in place, the permitted requirement may not be sufficient for modern amenity use.  Water companies in Wales will work with the environmental regulator to determine assessment criteria and then carry out assessments by the end of July 2023. These assessments will identify where further screen installation is required and will inform companies' case for investment in AMP8 and subsequent investment programmes. These investment programmes are provided to the economic regulator Ofwat every five years and are challenged for both provision of the service provided and the affordability of the plans.

The scale of this investment could be significant. Across Wales there are over 2400 storm overflows, and it is estimated that up to half will require some form of improved screening provision. The rural nature of a significant proportion of the network in Wales, some storm overflows are in remote locations, with no power supply.  and therefore the installation programme will be complex and require time to design and install safely. Affordable targets will be set and reviewed as part of that investment planning process.

Working with regulators and Welsh Government, Water Companies will be expected to identify and prioritise action at those assets that are deemed to require urgent and immediate attention, re-prioritising expenditure already agreed for the AMP7 Business Plans. 

Our commitments

The actions being taken forward within this workstream are all aligned to the Welsh Government Programme for Government 2021-26 and the Wellbeing goals of:

  • Building a stronger, greener economy as we make maximum progress towards decarbonisation.
  • Make our cities, towns and villages even better places in which to live and work.
  • Embed our response to the climate and nature emergency in everything we do.
  • Begin to designate Wales’ inland waters for recreation, strengthening water quality monitoring.
Lead Organisation Action Why? By When
NRW We will review the provision of screen requirements in the “how to comply with your environmental permit” guidance noted above. To ensure the standards required of water companies are based on modern design standards and sound evidence  This action aligns with actions in the regulation action plan. To be reviewed in line with the PR24 timetable submissions.
DCWW/HD We will undertake assessment of our permits against our asset base to define the size of the programme required to provide evidence for target setting. To understand the scale of the problem and the investment required to improve levels of screening on storm overflows. The review will be complete by the end of July 2023

We will set targets for the installation of screens on storm overflows according to the required modern design standard.

To reduce the visual impact and long-term effects of items such as rag, wet wipes and other disposable, non-degradable matter have on the environment. We will carry out the review and publish targets by the end of December 2023
DCWW/HD We will ensure provision is made for the installation of screens during AMP8 (2025 to 2030) and beyond, according to the agreed targets.   To reduce the visual impact and long-term effects of items such as rag, wet wipes and other disposable, non-degradable matter have on the environment. September 2023


Targets and Water Company Investment programmes will be reviewed on a 5-year cycle, as part of the investment planning process. To ensure an affordable balance of investment priorities. Each 5-year investment cycle
DCWW/HD We will install screens at the appropriate assets according to updated design standards and will prioritise the installation in high priority rivers To reduce the visual impact and long-term effects of items such as rag, wet wipes and other disposable, non-degradable matter have on the environment. 100% installation of screens by 2050; with high priority screens installation by 2040.