Welsh Water recorded its worst ever result for serious pollution incidents in 2025
Welsh Water recorded its worst ever result for serious pollution incidents in 2025, with more than half caused by a single failing pipe running through a protected nature reserve in south Wales.
The figures are contained in the company’s annual Pollution Incident Reduction Plan, a document all water and sewerage companies are legally required to publish each year.
Welsh Water recorded 11 serious pollution incidents in 2025, compared with 6 in 2024 — an 83% increase and, according to the plan, the company’s poorest result on record by this measure.
Natural Resources Wales gave Welsh Water a Red rating for serious incidents, a status it shares with five other water companies across England and Wales.
Six of the 11 serious incidents came from one asset: the rising main serving Marlas sewage pumping station, which runs through the Kenfig Nature Reserve SSSI near Port Talbot.
The pipe has repeatedly burst since August 2023.
Welsh Water said in the plan that the deterioration in its serious incident figures was largely driven by that single asset.
Work to replace approximately 4.5km of the Marlas main is under way, with completion expected in November 2026.
The same document shows Welsh Water is the worst-performing water and sewerage company in England and Wales for self-reporting — alerting regulators to pollution incidents the company detects itself, rather than waiting to be notified by a third party.
Welsh Water reported 74% of relevant incidents to regulators in the most recent comparative period.
The best-performing companies reported between 88% and 92%.
The total number of wastewater pollution incidents did fall in 2025 — from 132 to 111, a 16% reduction and the first decrease since 2020.
The company’s regulatory target for the year was 92 incidents.
Welsh Water said in the plan: “complexity is not an excuse,” adding that it accepts accountability for the condition of its assets and their impact on rivers, coastal waters and the wider environment.
Welsh Water cautioned that the 2025 figures have not yet been finalised with Natural Resources Wales and the Environment Agency, and remain subject to change.
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