Almost every monitored river in the Medway and the Stour now fails the legal environmental tests. Eleven Kent sewage treatment works are running close to the limit. The average Southern Water customer’s bill is set to rise 53% by 2030. This is the plain-English guide to what is actually happening to Kent’s water — and what it means for the people who live here.

This is the reader-edition companion to Kent Local News’s five-part investigation into Kent’s water and sewage networks. The longer professional version published on Monday 4 May. This version covers the same ground — but written for anyone who has ever had to pay a water bill, walked along a Kent river, or wondered why a planned new housing estate has been stuck for years. Subsequent parts publish Mondays and Thursdays through May.

How bad is it, really?

The Environment Agency uses a five-band scale — from High to Bad — to grade the health of every river, lake and coastal water body in England. To pass at “Good”, the water has to be clean enough, healthy enough for wildlife, and flowing properly.

Across England, only one in seven monitored water bodies passes that test. In Kent, the picture is much worse. In the Medway basin, 97 out of every 100 monitored water bodies fail. In the Stour, all of them do. The Darent and the Cray, Kent’s western chalk-stream system, are in similar shape.

This is not just a story about wildlife. The same legal tests that flag up failing rivers are also the tests that block building permissions, trigger warning notices on beaches, and push up your water bill.

Why your water bill is going up by 53%

The water industry runs on five-year regulatory cycles called AMPs. The current cycle, AMP8, runs from 2025 to 2030. In December 2024 the regulator Ofwat published its final decision on what each water company is allowed to charge over those five years.

Across England and Wales, the average household will pay an extra £157 by 2030 — a 36% rise in real terms. Southern Water customers will pay much more: a 53% rise, the highest of any water company in England and Wales. That works out at roughly £200 to £300 a year extra for a typical Kent household by 2030, on top of inflation.

Southern Water had asked Ofwat for permission to raise bills by 83%. Ofwat said no, but agreed to 53%. The money is supposed to fund the largest environmental upgrade in the history of the UK water industry — about £104 billion across the country, with about £12 billion of that going on stopping sewage spills.

The sewage figures are worse than you think

Water companies are allowed to release untreated sewage during heavy rain, through what are called storm overflows. The Environment Agency now monitors all 14,254 of these in England.

In 2023, the most recent full year of public data, water companies in England released untreated sewage for 3.61 million hours combined. Southern Water alone — the company serving Kent — was responsible for 317,000 of those hours, or nearly one-tenth of the national total. The 2024 figures, published by the Environment Agency in March 2025, were worse again: a small further increase in spill duration, and the regulator’s own description of an “all-time high”.

Some individual storm overflow points in Kent recorded spill durations of more than 8,000 hours in a single year — the maximum physically possible is just over 8,760. In other words, those overflows were spilling almost continuously.

What is wrong with Kent’s bathing water?

The Environment Agency rates designated bathing waters as Excellent, Good, Sufficient or Poor each year. Anywhere classified Poor triggers a statutory advice-against-bathing notice for the season.

In the most recent classification (the 2024 list), Dymchurch was rated Poor. Walpole Bay, which had been Poor in earlier years, recovered to Good in 2024 — proof that recovery is possible if the right work is done. But the broader pattern across Kent’s coast is precarious, with Southern Water’s wastewater treatment performance and agricultural runoff identified as the main pressures pushing classifications down.

Why councils can’t build the homes the government wants

Central government has set Kent’s councils housebuilding targets that, in some cases, exceed what the local water network can physically supply.

The clearest example came in March 2026, when South East Water wrote to Tonbridge & Malling Borough Council. The council is mandated to deliver 19,620 new homes by 2040. South East Water’s formal letter said it could supply tap water for 6,318 of them — less than one in three.

The same problem is showing up at the sewage end. Southern Water’s long-term plan, published in 2024, names eleven Kent treatment works that are at risk of breaching their dry-weather-flow limits if planned growth goes ahead. The named sites include Motney Hill (Medway), Aylesford (Maidstone catchment), Tonbridge, and both treatment works serving Royal Tunbridge Wells. When a treatment works hits its limit, the council can’t legally permit any more development in that catchment without solving the capacity problem first.

The Stodmarsh story — and why it just got better, a bit

The Stodmarsh nature reserve, north-east of Canterbury, has been the most visible case of this kind. Since 2020, more than 7,000 planned new homes across Kent have been blocked because the sewage works in the Stour catchment can’t take any more nutrient pollution without breaching Stodmarsh’s legal protections.

That has now started to shift. On 24 April 2026, Natural England approved a new offset scheme called the Stodmarsh Stream Enhancement Scheme. Run by Greenshank Environmental, the scheme restores 2.5 km of agricultural ditches into more natural streams that filter out nitrogen and phosphorus before they reach the Stour. That generates “credits” that developers can buy to offset the pollution from their new homes.

The first phase is expected to release enough credits for between 3,000 and 5,000 homes across Ashford, Canterbury and the wider catchment. A second phase would extend that to 8,000. The work is locked in for more than 80 years.

That is a big deal for Ashford and Canterbury. But it is one piece of a much bigger problem. Greenshank itself estimates that more than 160,000 homes are still blocked nationally by similar nutrient-neutrality rules — meaning Stodmarsh, even fully resolved, accounts for around five per cent of the backlog. And it does nothing for the eleven Kent treatment works heading for their dry-weather limits.

What this means for your weekly life

If you live in Kent, this story affects you in three concrete ways.

Your water bill is going up sharply. A 53% real-terms rise across the next five years is the biggest sectoral rise of any water company in the country. The first big jump arrived in April 2025; further annual increases are scheduled through to 2030.

Local building plans will slow down or stop. The Stodmarsh easing helps Ashford and Canterbury. But Tonbridge & Malling, Maidstone, Swale and Folkestone & Hythe each face their own version of the capacity wall. That means fewer affordable homes coming through the local pipeline, and more pressure on the existing housing market.

Kent’s coast and rivers are at the limit of recovery. Recovery is possible — Walpole Bay’s 2024 return to a Good classification proves it. But it requires investment delivered at pace, and on the current evidence the pace is not yet matching the scale of the problem.

What’s coming next in this series

Over the next four weeks Kent Local News will publish the rest of the investigation:

  • Part 2 (Mon 11 May): The housing-capacity gap in detail — what councils across Kent have actually been told they can build, and what the numbers say about the next decade.
  • Part 3 (Mon 18 May): Where the demand comes from — the demographic engine driving Kent’s growth pressure, and what the Office for National Statistics actually projects.
  • Part 4 (Mon 25 May): The bigger picture — the cumulative impact of growth on water, land, climate and wildlife in Kent.
  • Part 5 (Mon 1 June): A practical path to capacity — the proposals being put forward by ten political parties active in Kent, and a side-by-side assessment of what each one would actually do.

The next part publishes on Monday 11 May.