Southern Water Services Limited is the regulated water and sewerage company for South East England.
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Southern Water's gross Scope 1 and 2 emissions were flat between 2022–23 and 2024–25 (152,364 t to 152,320 t, location-based), and its Scope 3 rose about 35% year on year. Its 2025–26 report shows Scope 1 and 2 of 290,160 t, mostly because the industry changed how it counts nitrous oxide from sewage treatment; without that change, Scope 1 would have risen 1.5%. The Environment Agency rated it 2 stars for 2024, with 15 serious pollution incidents, and its three-year average leakage missed its target. In 2025 it pleaded guilty to 13 offences at Margate and Broadstairs and was fined £7,127,083 in July 2026. In 2021 it was fined a record £90m for almost 7,000 unpermitted sewage discharges.
Southern Water scores 37/100 (Below expectations) on SINK's independent climate assessment, scored from public data only. Fees pay for the review, never the result. Last verified October 2026.
That places Southern Water joint 435th of 847 companies scored, and joint 9th of 11 in Water & Sewerage.
Where Southern Water sits among water & sewerage peers.
Among the 11 major water & sewerage brands we've scored, Southern Water is tied =9th of 11, with 1 other.
Its three lowest-scoring questions, and what the evidence didn't show.
Gross Scope 1–3 emissions rose 11.6% from baseline.
The full reasoning is in the ten questions below.
2021: £90m fine after guilty plea to 51 counts, nearly 7,000 unpermitted sewage discharges (2010–15), evidence of misleading regulator.
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Get in touch →Strongest on Carbon Footprint — Operations and Carbon Footprint — Supply Chain (7/10, 6/10). Weakest on Emissions Trajectory and Water Impact (1/10, 2/10).
The 3 companies in the sector scoring nearest above Southern Water.
Northumbrian Water's net market-based operational emissions fell from 68.6 to 15.9 ktCO2e between 2019/20 and 2024/25, relying on renewable electricity and gas certificates, while gross location-based emissions moved from 163.3 to 152.6 kt.
See the breakdown →Anglian Water's gross reported emissions rose from 265,219 to 297,156 tCO2e between 2022/23 and 2024/25.
See the breakdown →Yorkshire Water's market-based emissions rose from 281 to 295 ktCO2e between FY2024 and FY2025, and Scope 1 rose from 85 to 88 kt.
See the breakdown →The formula and all 10 sources.
Same ten questions for every company. No private weighting.
SINK = (0.3 × Base + 0.7 × Performance) × Scale10 sources used in this assessment. All publicly available. Each row shows which of the ten questions it informed.
“assured by independent consultants in accordance with the methodology of the AA1000 Assurance Standard v3”
“This requests that our suppliers provide us with details of”
“For 2024: red status for 2 metrics, amber status for 3 metrics and green status for 2 metrics”
“we recorded 269 category 1-3 pollution incidents in 2024, a 15% increase in pollution incidents compared to 2023”
“The total fine is therefore £7,127,083.”
“This year’s significant increase in Scope 1 emissions is primarily due to sector-wide updates to two carbon emission factors within the Ofwat Carbon Accounting Workbook.”
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Southern Water Services Limited is the regulated water and sewerage company for South East England. It was incorporated on privatisation in 1989 and is headquartered in Worthing. Its filed accounts for the year to 31 March 2026 report revenue of £1,443.2m and an average of 3,109 employees. It is regulated by Ofwat and the Environment Agency.
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