The Cwm Taf Water Supply Strategy is about future proofing our water supply to customers and communities.
In Wales we are fortunate to have the natural resources that provide us with an essential supply of water, but we never take that for granted. To make sure we keep our water flowing and provide safe clean drinking water, we need to invest to modernise our network so we can adapt to future pressures on water resources.
The need for new water treatment facilities
Our water treatment facilities in the Bannau Brycheiniog National Park provide drinking water to people across Merthyr Tydfil and the surrounding areas. 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. Over the years we have upgraded and refurbished the works to make the best use of our assets in their current location, it is now becoming increasingly difficult and costly to maintain these works.
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.
New facilities will need to provide:
- New and improved water treatment process, supplying consistently high-quality water.
- Additional water storage to make sure we have a reliable supply of water.
- Future proofed facilities to cater for future population growth and to be more resilient to the effects of climate change.
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.
Our investment proposal
We’ve spent time considering the options available to us and:
- undertaken numerous surveys,
- completed site selection processes,
- and consulted on our proposals with the local community and stakeholders in Merthyr Tydfil and the Bannau Brycheiniog National Park.
This process helps inform our decisions to find the best solution to modernise our water treatment facilities for our customers now – as well as those in the future.
See Our Consultations section to find out more.
You can view our Site Selection Report 2024 (revised proposals) here.
We believe that our proposals will provide a sustainable solution to replace our ageing facilities and provide new and resilient water treatment processes to meet our legal duty whilst also minimising the environmental impacts and costs to our customers.
The investment has been separated into two proposals and involves a split-site approach, which means we have to deliver both proposals set out below, to provide a solution to the Drinking Water Inspectorate legal notice.
Proposal 1: Dan-y-Castell Water Treatment Works and Pontsticill Pumping Station
Constructing a new water treatment works at Dan-y-Castell Farm in Merthyr Tydfil, along with a new raw water pumping station at our Pontsticill site. This proposal will replace the existing Pontsticill Water Treatment Works.
Proposal 2: Llwyn-onn Water Treatment Works Upgrade
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.
Together the plans will modernise the drinking water network across South Wales, replacing century-old treatment facilities and increasing clean water storage capacity.
We’ve created two website pages, one for each proposal. You can access further information on the relevant proposal by clicking on the sections below.
Next steps
For us to meet our legal duty and to progress with our proposals to invest in our water treatment facilities, we’ll first need to seek planning permission. This requires us to submit separate planning applications for each proposal to the two relevant planning authorities, Merthyr Tydfil County Borough Council and Bannau Brycheiniog National Park Authority.
Before we submit our planning applications we’re:
- Carefully reviewing and taking into consideration the responses to our consultations.
- Conducting further surveys to inform our planning applications.
- Working closely with specialist consultees to consider the environmental and heritage impacts and disruption to communities – and understand how we can further avoid or mitigate these impacts.
Community engagement: We understand that our proposals are of interest to the local community and we would like to encourage your continued collaboration and feedback to help us identify how we can minimise disruption and deliver positive outcomes.
We are keen to work in collaboration with the local community as we develop our plans to create sustainable places and support improvements to the local environment and biodiversity. This could be supporting educational activities, voluntary organisations or health and wellbeing initiatives.
If you would like to engage with us, please email cwmtafproject@dwrcymru.com.
Frequently Asked Questions
We appreciate there are lots of questions about this project and why we need to do it. We're currently producing a Frequently Asked Questions page which will be available soon.
- Should you have any queries then please email us cwmtafproject@dwrcymru.com
Our consultations
Our consultation period has now ended. We would like to thank everyone who took the time to engage with our consultations, and we greatly appreciate the feedback. We’re carefully reviewing the responses we received.
Statutory Pre-application Consultations: 30th October 2025 – 5th January 2026
We held two statutory pre-application consultations on our proposals to invest in new and resilient water treatment works and associated facilities.
The consultations provided the opportunity for the local community and stakeholders to review our plans, draft planning applications and to provide comments ahead of us applying for planning permission.
The feedback received as part of the pre-application consultation is being taken into consideration as we finalise our applications. The comments raised, and how we considered them, will form part of the final planning submissions – set out in the Pre-application Consultation (PAC) Reports.
Our pre-application consultations have now closed. The details of the proposals are still available to view on the links above.
Our Non-statutory Consultations 2022 & 2024
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, 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 non-statutory consultation brochure 2024 and non-statutory feedback report, which are available in the documents section below.