Sewage overflows affect harbour and beach water, and thousands of homes on the low-lying island depend on sea defences.
Raised by:Official data · Environment AgencyCouncil plans+2 moreSouthern Water (regulated programme set by the Environment Agency)Hampshire County Council (responsible authority, with local partners)
The issue in five minutes
The problem
Sewer storm overflow spills at or near Portsmouth: 329 counted spills (2025). Affects: Sea swimmers and water users, harbour wildlife and shellfish, and households and businesses in coastal flood-risk areas.3 related measures
1,520 hours Hours of sewer storm overflow spills at or near Portsmouth (2025)
86 spills Storm-overflow spills at Henderson Road, Eastney (2025)
2,849 properties Properties in the high river or sea flood-risk band (June 2026)
Different measures, sources and periods: shown together, not ranked against each other.
Who says so
Environment Agency.
What’s being done
Scrutiny review: sewage discharges into the seaReview sewage discharges into the sea around Portsmouth, taking evidence from Southern Water, the Environment Agency, the University of Portsmouth, campaign groups and Cabinet members, and report recommendations.Lead Portsmouth City Council scrutiny panelIn progress · evidence 3 November 2026
PR24 Water Industry National Environment ProgrammeCut spills from the Budds Farm, Havant storm overflow (permit A00751) into Langstone Harbour to fewer than 10 a year, with sustainable drainage and storage, to protect shellfish waters (WINEP action 08SO103182a).Lead Southern WaterNot verified
Funded by
Funded by Southern Water (customer bills, under Ofwat’s 2024-2030 price limits)Amount not stated · No Budds Farm cost is published
Show the other 1
Nutrient Neutral Mitigation StrategyRequire new homes to be nutrient neutral, so that wastewater from development does not add nitrates to the Solent, using mitigation credits under a section 111 agreement.Lead Portsmouth City CouncilIn progress · evidence 10 November 2026
Two counts, two selections. The 329 spills above are for the 18 overflows the water company lists inside Portsmouth (2025). The sewage tracker counts all 48 monitored outfalls into Portsmouth Harbour, Langstone Harbour and the Southsea and Eastney coast, which gives 443 spills for 2025. Neither is a swimming advisory; annual spills do not say whether a beach is safe on a given day. See the sewage tracker →
What is still missing
3 items not yet published or reported
Not yet published for the work above:
Storm overflow spill volumes around Portsmouth (Freedom of Information request)
Site list, dates and spend for Southern Water’s £170 million Portsmouth Harbour scheme (company pages are undated)
No like-for-like series of properties at flood risk, so flood exposure has no outcome rule. The Environment Agency re-issues its model in versions (the June 2026 and November 2026 versions are held), and differences between versions reflect model updates, not changing exposure
Sewer storm overflow spills at or near Portsmouth, compared over 3 years.
1 · The issue
What the evidence says
Who is affected: Sea swimmers and water users, harbour wildlife and shellfish, and households and businesses in coastal flood-risk areas.
RiskBeach water quality needs results, not just promises. Southsea East was rated Poor for 2025. The Henderson Road, Eastney overflow recorded 86 overflow spills during 2025. The beach classification and overflow monitor cover different things. A discharge count cannot attribute every poor water sample to that outlet.In context →
RiskFlood protection needs delivery and maintenance. The June 2026 assessment places 2,849 properties in the high river or sea flood-risk band. This is modelled exposure, not an annual count of flooded homes. Coastal schemes can reduce risk, but their operation, maintenance and future climate assumptions remain important.In context →
2 · The evidence
The figures
329 counted spills
Sewer storm overflow spills at or near Portsmouth Wider area 2025Environment Agency ↗ · retrieved 9 Nov 2026
Sewer storm overflow spills at or near Portsmouth
2020 to 2025
Overflows at or near Portsmouth · counted spills
Reviewed figures: 2020 to 2025.
Change dates and range
Shown on this chart: From 2020 to 2025, sewer storm overflow spills at or near Portsmouth fell by 6.8% in Overflows at or near Portsmouth and fell by 27.6% in England (all companies).
Both places compared over 2020 to 2025, using matching published dates.
Compared areas: Overflows at or near Portsmouth; England (all companies).
Change since 2020 (%)
Overflows at or near PortsmouthEngland (all companies)
-34.6%0.5%35.6%
20202025
Each line joins consecutive published observations for that place. Missing dates remain gaps.
Hover or tap the chart for a value. Use the date slider with touch or arrow keys. Escape closes the chart label.
Sewer storm overflow spills at or near Portsmouth: 16% change between 2022 and 2025, smaller than the threshold used (Standard deviation of the five year-to-year changes in counted spills, 2020 to 2025 (66.7 spills, rounded up to 67). Spills depend heavily on rainfall, so only changes larger than normal weather-driven variation are treated as real.).
Rule: Standard deviation of the five year-to-year changes in counted spills, 2020 to 2025 (66.7 spills, rounded up to 67). Spills depend heavily on rainfall, so only changes larger than normal weather-driven variation are treated as real.
Same period, other places (2025)
Overflows at or near Portsmouth329
Southern Water (all overflows)15,554
England (all companies)292,119
Comparators: the nearest cities and the most similar places, with England.
More trends for this issue (1)
Hours of sewer storm overflow spills at or near Portsmouth
2020 to 2025
Overflows at or near Portsmouth · hours
Reviewed figures: 2020 to 2025.
Change dates and range
Shown on this chart: From 2020 to 2025, hours of sewer storm overflow spills at or near Portsmouth fell by 44.3% in Overflows at or near Portsmouth and fell by 39.4% in England (all companies).
Both places compared over 2020 to 2025, using matching published dates.
Compared areas: Overflows at or near Portsmouth; England (all companies).
Actual values
Overflows at or near PortsmouthEngland (all companies)
01,951.7k3,903.5k
20202025
Each line joins consecutive published observations for that place. Missing dates remain gaps.
Hover or tap the chart for a value. Use the date slider with touch or arrow keys. Escape closes the chart label.
Where sewage is discharged, and what the water tests show
Explore monitored outfalls, discharge frequency and duration, and the official tests at nearby bathing waters. These measures show different parts of the evidence.
Recorded spill counts across 48 outfalls, 2025
443
Counted with the 12/24-hour method. Several outfalls spilling at once each add to the count, so this is not the number of separate events in the city.
Summed spill duration, 2025
1,848 outfall-hours
Hours added up across outfalls. It is not the time the water was polluted, and it is not a volume. Monitors recorded 97.9% of the year on average.
Based on four seasons of samples. A measured result is a different thing from a recorded discharge.
Recorded spill counts across selected outfalls, by year. The outfalls monitored changed over time, so the full page also shows the same outfalls in every year. This counts every outfall into these waters, so it is higher than the headline figure above, which counts only the overflows the water company places inside the city. Data from the Environment Agency, checked 2026-11-10.
Explore the water evidence →Map, year-by-year counts and duration, monitoring coverage, bathing-water results and tables.
3 · What residents say
Residents’ evidence
0 surveys
Not yet known: No published survey of Portsmouth residents asks about this issue directly. General concern about an issue does not show support for any particular proposal.
23 October 2026output Large parts of Ports Creek and Hilsea Lines opened; work continues around Peronne Road Bridge, with full completion expected in autumn 2027. source ↗
Committed by Portsmouth City CouncilNot verified
Corporate Plan 2024-2026
Continue to lobby and work with partners to improve air and water quality and city biodiversity.
ApprovedFundedUnder wayCompleted
No dated evidence of progress has been found; stages are shown hatched.
21 July 2026outcome Carbon Action Plans reported to Cabinet for information: council emissions of 7,885 tonnes CO2e in 2024/25, Scope 1 and 2 about 60% below 2012/13; city emissions down 52% since 2005. source ↗
1 October 2026outcome Air quality annual status report (information only): in 2025 one diffusion tube exceeded the annual nitrogen dioxide limit (Alfred Road, 41.86 µg/m³, kerbside, not a place of relevant public exposure, so no new management area); 225 of 228 tubes show a downward trend over 2021-2025. source ↗
10 November 2026output The council’s water quality page describes two solar-powered LED signs on Eastney seafront, red if sewage was released in the last 48 hours, Environment Agency warning signs at Southsea East, and Yellow Fish drain markers, working with Southern Water and the Environment Agency. source ↗
Committed by Portsmouth City Council scrutiny panelIn progress
Scrutiny review: sewage discharges into the sea
Review sewage discharges into the sea around Portsmouth, taking evidence from Southern Water, the Environment Agency, the University of Portsmouth, campaign groups and Cabinet members, and report recommendations.
7 September 2026milestone Southern Water, the Environment Agency and the University of Portsmouth gave evidence. Southern Water said 43 projects across Portsmouth aim to remove about 50 hectares of hard surface draining to sewers, ten completed, and that the Western Interceptor extension is at design stage, due to start in January 2028. source ↗
5 October 2026milestone The Final Straw Foundation gave evidence, asking for more frequent testing at more locations, faster results and measurable targets. Action recorded: a meeting between the foundation and Southern Water, with no date set. source ↗
3 November 2026milestone Cabinet members for climate change and for community safety gave evidence; a local resident’s written views were published. Minutes not yet published. source ↗
Committed by Portsmouth City CouncilNot verified
Surface Water Management Plan
Reduce surface water flood risk in the fourteen hotspot areas identified in the Surface Water Management Plan (September 2025 update).
ApprovedFundedUnder wayCompleted
No dated evidence of progress has been found; stages are shown hatched.
Require new homes to be nutrient neutral, so that wastewater from development does not add nitrates to the Solent, using mitigation credits under a section 111 agreement.
PR24 Water Industry National Environment Programme
Cut spills from the Budds Farm, Havant storm overflow (permit A00751) into Langstone Harbour to fewer than 10 a year, with sustainable drainage and storage, to protect shellfish waters (WINEP action 08SO103182a).
ApprovedFundedUnder wayCompleted
No dated evidence of progress has been found; stages are shown hatched.
Who pays, key dates and what is missing
Funded by
Funded by Southern Water (customer bills, under Ofwat’s 2024-2030 price limits)Amount not stated · No Budds Farm cost is published; Southern Water’s 2023 business case puts its whole 2024-2030 storm overflow programme at £682m
Southsea Coastal Scheme: Frontage 6, South Parade Pier to St George’s Road
The next stretch of the Southsea coastal flood defences.
Whose project
Run by Portsmouth City Council (Coastal Partners)
Stage
Construction expected to begin in spring 2027 and finish in late summer 2028 (scheme website). Public drop-in events were held on 23 and 24 October 2026. Includes a raised promenade, walking and cycling routes, crossings, lighting and seating. (10 November 2026, Find out more about the next phase of Southsea’s coastal defences ↗)
Where, funding and what would show it worked
Where
Southsea seafront, South Parade Pier to St George’s Road · Southsea seafront.
Funding
No funding published.
Next check
Start of works and the phase cost.
Note: Part of the existing Southsea Coastal Scheme record; its cost is not counted again. The user’s lead described this frontage as South Parade Pier to St George’s Road; the scheme bulletin says Speakers’ Corner to St George Road.
1 earlier value
10 November 2026: Extent and dates was “Southsea Coastal Scheme: next frontage, Speakers’ Corner to St George Road; Due to begin in spring 2027 (scheme bulletin). The finish date was not confirmed.”, now “Frontage 6, South Parade Pier to St George’s Road; spring 2027 to late summer 2028” (source)
Outside the city · waterProposed
Hampshire Water Transfer and Water Recycling Project
Southern Water’s proposal to recycle treated wastewater and transfer water across Hampshire, needing a Development Consent Order.
Water recycling plant off Harts Farm Way, Havant, with pipelines to Bedhampton Springs and Otterbourne · Mostly outside Portsmouth; uses the existing Eastney outfall, pumping station and transfer tunnel in the city.
Funding
No funding published.
Next check
Examination outcome and the Secretary of State’s decision.
Publish one dated record of every Southsea and North Portsea coastal frontage, from design to completion, then show who inspects and maintains each defence, how upkeep is funded and what flood risk remains afterwards.
Start soonBuild nextLonger term
EstimateAllocatedSpentUnknown
Proposed lead: Portsmouth City Council (proposed), as the lead authority for both schemes, with Coastal Partners preparing the register
First step: Anyone, including UK Facts, can compile the frontage list from the two scheme websites today.
Outcome: Sewer storm overflow spills at or near Portsmouth, latest against 3 years earlier; changes smaller than 67 are treated as no clear change. Now: no clear change.
Connect water-company work to beach water results: Counted spills and hours at each listed overflow; Improvement actions completed by their deadline; Bathing water classification; Pollution risk warnings at Southsea East.
Track coastal protection through completion and upkeep: Coastal sections completed; Properties in the high river and sea flood-risk band; Defences with a published inspection and maintenance arrangement; Upkeep spent compared with planned upkeep.
What is not yet known
Storm overflow spill volumes around Portsmouth (requested under Freedom of Information)
Site list, dates and spend for Southern Water’s £170 million Portsmouth Harbour scheme (company pages are undated) (not published)
No like-for-like series of properties at flood risk, so flood exposure has no outcome rule. The Environment Agency re-issues its model in versions (the June 2026 and November 2026 versions are held), and differences between versions reflect model updates, not changing exposure (not published)
Cost of living is featured by editorial choice. Other issues follow the order respondents gave the council in its 2025 budget consultation, a survey people chose to take part in; it describes respondents, not all residents.
