Our water treatment works in the Bannau Brycheiniog National Park provide drinking water to people across Merthyr Tydfil and the surrounding areas. The investment project in this area is called the Cwm Taf Water Supply Strategy, future proofing our supply of water to our customers.
The drinking water network in this area includes a number of water treatment works, many of which were built in the early 1900s.
The water treatment works at Pontsticill, Cantref and Llwyn-onn are ageing and have become increasingly difficult to maintain. We now have a legal duty to upgrade the water treatment processes, providing a sustainable solution to supply clean drinking water well into the future.
Without major investment, we will not be able to continue to meet the high drinking water standards we must comply with, and customers will be at risk of increased water supply interruptions in the future.
We’ve spent time considering the options available to us, whilst also consulting with the local community and stakeholders on our proposals, to help inform our decisions and find the best solution to modernise our water treatment facilities.
We’re now consulting on our proposals which we believe will provide the best solution to invest in and replace our ageing water treatment facilities to meet our legal duty whilst also minimising the environmental impacts and costs to our customers.
Welcome to our consultations
30th October – 10th December 2025
We have launched two statutory pre-application consultations, designed to share with you, the need for the investment and our proposals to invest in new and resilient water treatment works and associated facilities.
Our one proposal involves building a new water treatment works at Dan-y-Castell Farm in Merthyr Tydfil, close to the A465 Heads of the Valleys Road, along with a new raw water pumping station at our Pontsticill site, to replace the existing Pontsticill Water Treatment Works.
Whilst our other proposal involves investing in and upgrading the existing Llwyn-onn Water Treatment Works, which will allow the decommissioning of Cantref Water Treatment Works that was originally built back in 1926.
We’re consulting on each proposal separately and we’ll need to submit two separate planning applications, one for each proposal, to the relevant planning authorities: Merthyr Tydfil County Borough Council and Bannau Brycheiniog National Park.
Together the plans will modernise the drinking water network across South Wales, replacing century-old treatment facilities and increasing clean water storage capacity.
We want to hear your views
These consultations provide the opportunity for the local community, our customers and stakeholders to review our plans and draft planning application documents, and to provide comments ahead of us applying for planning permission.
The feedback received as part of these consultations will be taken into consideration as we finalise our applications. The comments raised, and how we considered them, will form part of our final planning application submission - set out in the Pre-application Consultation Reports.
Prior to providing us with your feedback, please take the time to view our consultation materials.
We’ve created two website pages, one for each proposal. You can access these pages by clicking on the sections below.
Each site has a virtual consultation room, containing information on the relevant proposal. Please make sure you visit the additional information on the main table within the virtual consultation room, which contains a link to the interactive map and the online feedback form. There are also two screens in each room, that contain an introductory film, visualisations and a computer-generated fly-through to help you understand how the developments could look.
A suite of draft planning documents is available on each site for you to review.
You will find details on how to send us your comments on consultation sites below. There are separate forms for each proposal so we can ensure that any feedback received will be specific to each proposal. We have colour coded the forms for clarity.
We welcome and encourage feedback on both proposals, for those who wish to comment on both you will need to complete the two feedback forms.
Meet the team
Come to one of our public information events to speak to the team, ask questions and learn more about our proposals and why we need to deliver them.
Our consultation events:
- Thursday 6th November - 3pm-6pm at Pontsticill Memorial Hall, Vaynor Road,CF48 2RU
- Thursday 13th November - 2pm-7pm at Cefn Coed Community Hall, New Church Street, CF48 2NA
- Wednesday 26th November - 3pm-6pm at Nant Ddu Lodge & Spa, CF48 2HY
- Thursday 4th December - 1pm-5:30pm at Merthyr Tydfil Central Library, High Street, CF47 8AF
Further information
Frequently Asked Questions
We appreciate there will be lots of questions about this project and why we need to do it, should you have any queries then please email us cwmtafproject@dwrcymru.com.
We will be updating this section throughout the consultation period responding to the frequently asked questions.
Our previous non-statutory consultations
Original proposal: Single-site Water Treatment Works 2022
In 2022, we held a non-statutory consultation on early proposals to replace the three existing water treatment works with a single-site new water treatment works on Gurnos Farm, Merthyr Tydfil, and invited the local community and stakeholders to comment on this proposal.
The feedback we received was extremely useful. Following the 2022 consultation, we spent time listening to the local community’s feedback and challenged ourselves to see if there were other solutions which balanced our need to meet our legal duty to improve the local water infrastructure whilst also considering the community’s feedback and environmental impacts.
Revised proposals: Split-site approach 2024
In 2024, we held a further non-statutory consultation on our revised proposals, that together will provide new and resilient water treatment facilities, safeguarding and future proofing the supply of water to present and future generations, whilst removing the need for a larger single-site treatment works on Gurnos Farm.
By taking additional time to review and conduct further surveys, we were able to revise our proposals offering a split-site approach, which means proposing to upgrade the existing Llwyn-onn Water Treatment Works and constructing a new smaller water treatment works at Dan-y-Castell Farm, Merthyr Tydfil, along with a new raw water pumping station at our existing Pontsticill Water Treatment Works site.
The split-site approach allows us to:
- Upgrade one of the existing water treatment works and re-use existing Welsh Water assets.
- Reduce the size of a new water treatment works required in the Merthyr Tydfil area.
- Minimise the amount of new pipework and pumping stations needed, protecting heritage and minimising traffic disruption.
- Reduce capital costs and the cost to our customers.
- Provide a lower embodied carbon solution by maximising the use of existing infrastructure.
Further information on these proposals is available in the Cwm Taf Water Non-statutory Consultation Brochure 2024, which is available in the previous documents section below.
We would like to thank everyone who took the time to engage with the non-statutory consultation process, the feedback that we received has been greatly appreciated.
Read our non-statutory feedback reports here:
PDF: Dan-y-Castell non-statutory feedback report
PDF: Llwyn-onn non-statutory feedback report
What’s next
For us to meet our legal duty and to progress with our proposals to invest in our water treatment facilities, we will need to seek planning permission.
Following the pre-application consultations we’ll be finalising our planning documents prior to submitting separate planning applications for each proposal to the two relevant planning authorities, Merthyr Tydfil County Borough Council and Bannau Brycheiniog National Park Authority.
Pre-application consultations will close Wednesday 10th December 2025.