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About the Utility
Southern Water Services Limited is the appointed water and sewerage undertaker for a region spanning Kent, Sussex and Hampshire. Since 2021 its ultimate holding company, Greensands, has been majority-owned by funds managed by Macquarie, which have put new equity into the regulated company. Ofwat sets its prices and performance commitments, the Environment Agency oversees its environmental permits and the Drinking Water Inspectorate its water quality. The company carries a heavy enforcement legacy, including a record £90 million fine for illegal sewage discharges and £126 million of penalty and rebates from Ofwat’s 2019 enforcement action. Ofwat’s latest price review still found its performance lagging behind most other companies.
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Water System
Recent Drinking Water Inspectorate summaries record 86 treatment works and a mains network of 13,866 km. Water quality remains under formal improvement programmes: one notice requires action on rising source-water nitrate at Falmer and other works serving Brighton by March 2027, while a separate programme addresses network water quality and operating procedures. Operational performance has also been persistently weak. In 2019-20 Southern Water was the only company to miss its leakage commitment, and its supply interruptions in 2022-23 far exceeded the five-minute level Ofwat had set as the target for the end of that price control.
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Wastewater System
Wastewater is the company’s most exposed service. The Environment Agency has rated its sewerage pollution incidents red in every assessment since 2019, even though the incident rate has fallen from that year’s level, and serious incidents rose to 15 in 2024. Storm overflows still spill frequently. In February 2026 Ofwat accepted enforceable undertakings to secure compliance with urban wastewater treatment regulations and the company’s licence, including £13.5 million of additional investment from Southern Water and its shareholders. Recent prosecutions for sewage pollution show that the legacy is not yet closed.
Sewerage pollution incidents
Category 1–3 incidents per 10,000 km of sewer, calendar years 2019–2024, Environment Agency assessment (every year rated red)
All values are Environment Agency actuals on one measure and calendar-year basis, as published in six annual company data reports.
Sources: Environment Agency, Southern Water EPA data reports 2019–2024.04
Investment & Priorities
Ofwat’s PR24 final determination, as republished, sets a total expenditure allowance of £8.69 billion for 2025-30, with funding for large and complex schemes contingent on more detailed cost information. Its determination was referred to the Competition and Markets Authority, which has since issued its final redetermination. The programme leans on shareholder support: the latest accounts report £900 million of additional group investment, with £300 million more committed after the year end, and no dividends have been paid to external shareholders since 2017-18.
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Key Challenges
- Reducing sewerage pollution incidents after six consecutive red Environment Agency ratings.
- Delivering the wastewater treatment compliance undertakings Ofwat accepted in 2026.
- Delivering the 2025–30 investment programme under a price control redetermined by the Competition and Markets Authority.
- Financing the programme through shareholder equity while net debt stands at 67% of regulatory capital value.
- Completing the drinking water quality improvement programmes required by the Drinking Water Inspectorate.