Cefn Dryscoed Water Treatment Works Upgrade
Statutory Pre Application Consultation
At Welsh Water, our priority is to provide every customer with a safe and reliable supply of clean drinking water. To achieve this, we continually review and upgrade our drinking water assets and processes across our water treatment works.
We are now planning essential improvements to Cefn Dryscoed Water Treatment Works. These upgrades will help improve the current water treatment process, improve water quality, reduce the risk of discoloured water, and ensure we continue to meet the high standards expected for drinking water in Wales.
Cefn Dryscoed water treatment works is located in Powys, within the Bannau Brycheiniog National Park, around 10km north of Hirwaun. It currently supplies drinking water to 6,487 properties in the Neath Valley area, using water from Ystradfellte Reservoir.
What work are we proposing?
We plan to upgrade the site by introducing a new treatment process known as a Dissolved Air Flotation plant. This new process will improve how solids and other particles are removed from the water source through first stage filtration.
The new treatment plant will be built on land next to the existing Cefn Dryscoed water treatment works. This will increase the size of the site by approximately 2424m2. The current site will continue operating while the new facilities are constructed.
Why is this work needed?
Some customers supplied by Cefn Dryscoed WTW have occasionally experienced discoloured water. This has been impacted by manganese, a naturally occurring mineral found in reservoirs. While manganese is not harmful at the levels found in drinking water, it can cause discolouration in water supplies. Construction of a new Dissolved Air Flotation plant will enable the second stage filtration to act as a dedicated manganese removal stage.
Upgrading the treatment process will allow us to remove more manganese and other particles before the water enters the network and on to your taps. Without this investment, these issues are likely to continue, and we may not be able to meet future drinking water standards.
This project will help ensure customers continue to receive a high quality, reliable water supply for years to come.
Programme details
The detailed design phase is currently underway and will be finalised before planning submission in July 2026. Subject to relevant planning approvals, construction work is scheduled between July 2027 and September 2028.
Will this affect my water supply?
No interruptions to the water supply from Cefn Dryscoed Water Treatment works are expected during the construction and commissioning of the new plant. There will be some construction activity on or near the site, but we will work to minimise noise, traffic, and any environmental impact.
Next steps
We are now consulting on our proposal, which we believe offers the best long term solution for maintaining high quality drinking water in the area and meeting our commitment to the Drinking Water Inspectorate (DWI).
Our statutory pre application consultation runs from XX February 2026 to XX 2026. During this period, you can view our draft planning documents and share your views with us before we submit a full planning application.
We want to hear your views
We welcome feedback from our customers, local community groups, stakeholders and anyone with an interest in the project.
Your comments will be carefully considered as we finalise our planning application. A summary of all feedback received—and how we have responded to it—will be published in our Pre Application Consultation Report, which forms part of the final planning submission.
Before sharing your views, please take time to read through the consultation materials and draft planning documents provided below.
We welcome and encourage feedback on our proposal, and you can provide your feedback by emailing CefnDryscoed@dwrcymru.com