01
About the Utility
Severn Trent Water Limited is the regulated water and sewerage business of the Severn Trent group, whose ultimate parent is Severn Trent Plc. Its present boundary dates from a 2018 realignment with Hafren Dyfrdwy, which moved the group’s activities in Wales to Hafren and kept those in England with Severn Trent. The Drinking Water Inspectorate recorded a supplied population of 8,606,000 in 2022. Ofwat sets its prices and service commitments under its PR24 price control, the Environment Agency assesses its environmental performance, and the Inspectorate enforces drinking water improvements through formal notices. Ofwat places the company in its standard financial resilience category and rated its latest annual performance average.
02
Water System
Severn Trent Water plans supply across 15 water resource zones. The Drinking Water Inspectorate recorded 130 treatment works in 2022, when surface sources provided 66.1% of the water supplied. Leakage is a relative strength: the three-year average beat its 2024-25 commitment, and losses sit below the national average as a share of water put into supply. Demand is moving the other way, with consumption per person rising in the latest year and household metering still below the national average. Drinking water compliance is the clearest weakness, as the Compliance Risk Index climbed far above Ofwat’s deadband in 2024.
03
Wastewater System
Severn Trent Water also collects and treats wastewater. For 2024 it was the only one of nine water and sewerage companies rated four stars by the Environment Agency, a rating it has held every year since 2019, and its treatment works met the compliance deadband throughout the last price control. Pollution remains the weak point. In 2024 sewerage pollution incidents were rated amber and missed the company’s performance commitment, while storm overflows averaged 25.4 spills each. The company reported a year-on-year fall in incidents for 2025-26, though two serious incidents occurred.
Sewerage pollution incidents
Category 1–3 sewerage pollution incidents per 10,000 km of sewer, calendar years 2019–2024, Environment Agency assessment
All values are Environment Agency actuals on one measure and basis, published as whole numbers, each taken from that year’s assessment.
Sources: Environment Agency, Severn Trent Water EPA data reports 2019–2024.04
Investment & Priorities
Ofwat’s PR24 final determination, amended in April 2025, gives Severn Trent Water a total expenditure allowance for 2025-30 that is significantly larger than its allowance for the previous five years, recovered through higher customer bills. Ofwat categorised the business plan as outstanding, carrying a reward. Named enhancement allowances cover storm overflows, nutrient pollution and drinking water quality. Funding combines new equity, raised before the period began, with rising debt: regulatory gearing reached 63.6% at March 2026.
05
Sustainability & Resilience
Resilience investment is steered by binding regulatory requirements. The Drinking Water Inspectorate requires an ultraviolet treatment solution for Cryptosporidium at Trimpley works and new iron treatment at Frankley works, and holds the company to undertakings on PFAS and lead for the current period. A bespoke capital carbon commitment covers roughly two thirds of the capital programme, and Severn Trent targets a 46% cut in Scope 1 and 2 emissions by 2031. Its catchment work with farmers, cited by the UK government, has avoided the need for expensive treatment works.
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Key Challenges
- Reducing sewerage pollution incidents, which missed the company’s 2024 commitment.
- Restoring drinking water compliance after the Compliance Risk Index rose far above Ofwat’s deadband.
- Delivering the £15 billion 2025–30 programme, including storm overflow and nutrient schemes.
- Containing household demand as consumption per person rises.
- Financing the investment step-up as net debt and gearing rise.
07
Major Projects
Trimpley UV treatment
Ultraviolet treatment to manage Cryptosporidium risk at Trimpley water treatment works, required by a Drinking Water Inspectorate notice.
- Status / period
- Design due 31 March 2027; construction and commissioning due 31 March 2030 (regulatory deadlines)
Frankley iron treatment
Solution for coagulation and clarification failure risks affecting iron and turbidity at Frankley water treatment works.
- Status / period
- Commissioning due 31 May 2027; completion report due 30 June 2028 (regulatory deadlines)
Minworth water recycling scheme
Water recycling scheme that Ofwat agreed Severn Trent Water will deliver in-house rather than through direct procurement.
- Status / period
- Delivery route approved in PR24 final determination