Cwm Taf Water Supply Strategy
Investing in new and resilient water treatment works and infrastructure to provide our customers with a safe, reliable supply of clean drinking water for decades to come.
The need for investment
Pontsticill Water Treatment Works provides water for approximately 188,000 customers every day – this includes households, businesses, and essential services such as hospitals and schools.
Originally constructed in 1927 it is now very dated, and the water treatment process need to be modernised. Over the years we’ve upgraded and refurbished the works to make the best use of our assets in their current location, however further upgrades are no longer possible, and it is becoming increasingly difficult and costly to maintain these works.
Due to its location within the valley of Pontsticill Village, as well a number of structures registered as Grade II Listed Buildings, Pontsticill Water Treatment Works cannot be upgraded and will need to be replaced and decommissioned.
Our proposal
We now need replace Pontsticill Water Treatment Works, which will ensure the continuity of water supply to our customers.
To do this we’re proposing to:
- Construct a new water treatment works at Dan-y-Castell Farm, Merthyr Tydfil, with treated water storage capacity, to maintain a reliable supply of clean water to customers.
- Construct a new pumping station within our water treatment works site at Pontsticill.
- Lay a network of new pipelines which will allow us to connect the new water treatment works to the existing network, as well as distribute clean water to homes and businesses.
This proposal will provide our customers with:
- A long-term solution to comply with our legal notice from the Drinking Water Inspectorate.
- New and improved water treatment processes to supply clean, safe water to our customers.
- Additional water treatment capacity to cater for future population growth.
- Additional water storage capacity to ensure we have a reliable supply of water.
- Future proofed resilient facilities to cater for the increasing effects of climate change.
For us to meet our legal duty and to progress with our proposal, we’ll first need to seek planning permission.
Timeline overview
Since we were issued our legal notice from the Drinking Water Inspectorate, we’ve spent time considering our options to find the best solution to modernise our water treatment facilities whilst also considering the environmental impacts, disruption to communities and costs to our customers.
The timeline below outlines the stages we have completed and an indictive timeline on what the next steps will be.
Next Steps
Testing and commissioning of the new water treatment facilities. Drinking water will then be distributed to homes and businesses from the new facilities.
We’ll then need to disconnect Pontsticill Water Treatment Works from the network, prior to decommissioning the existing facilities.
Subject to a planning decision, we have estimated that the construction of a new water treatment works, pumping station and associated infrastructure will take place over a 4-year period.
Stage 7 - Planning Application - 2026
As we prepare to 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.
We’ll need to submit our planning application to the relevant planning authorities; Merthyr Tydfil County Borough Council and Bannau Brycheiniog National Park.
Autumn/Winter 2025
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 application documents and to provide comments, ahead of us applying for planning permission.
We reviewed non-statutory consultation responses, carried out further surveys, and refined designs. This information supported the development of our draft planning application documents.
In January 2025, DWI updated the legal notice to specify a requirement to:
- Construct and commission the new water treatment works to replace Pontsticill.
- Upgrade Llwyn-onn Water Treatment Works and replace Cantref Water Treatment Works as part of the upgrade.
- Disconnecting Cantref and Pontsticill Water Treatment Works from the network, by September 2032.
Held non-statutory consultation on revised split-site proposals, inviting community feedback.
Announced decision to take additional time to review and consider our options. Reviewed feedback and undertook further surveys and updated site-selection process.
Held non-statutory consultation on the single-site proposal, inviting the community to comment on our early proposals. Published frequently asked questions.
Water supply is tightly monitored and independently regulated by the Drinking Water Inspectorate (DWI). This means we supply water that is safe to drink and meets the standards set out in the Water Quality Regulations.
Welsh Water was issued with a legal notice in 2019 by the DWI requiring us to upgrade the water treatment processes, at Cantref, Pontsticill and Llwyn-onn.
We carried out site selection review and ecology surveys to assess the option for a proposed single-site water treatment works.
Further information
We have produced some materials that have been designed to share with you the need for the investment, and what the new water treatment works and pumping station could look like.
Interactive map
Our interactive map, presented during our 2025 consultation, is still available to view. The map allows you to understand the location and layout of the proposed water treatment works and pumping station, and where we need to lay new pipelines.
The map allows you to navigate to locations of interest, and view images that have been embedded into the map (click on the circles). These images have been provided to show you the current view from that location, as well how the water treatment works or pumping station could look.
To access the interactive map click here.
Flythrough video & Computer generated images
Our fly-through video and computer-generated images, presented during our 2025 consultation, have been created to give you an idea of how the proposed Dan-y-Castell Water Treatment Works could look and how the design has considered the local landscape.
To access the fly through video click here.
These images are for illustrative purposes only.
Further visualisations will be presented within the Environment Statement we submit with our planning application. These images will be created for the Landscape and Visual Impact Assessment, which show the likely visual effects for the development from specific viewpoints.
Consultation brochures
Our consultation brochures can viewed and downloaded from our Cwm Taf Water Supply Strategy page, in the documents section here.
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
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 or call 0800 052 0130 and ask for a member of the Cwm Taf Water Supply Strategy to call you back. (General enquiries 8am-6pm Mon-Fri, 9am-1pm Sat).