Water bills across the Wessex Water region which includes Swanage and Purbeck are to go up by 21 percent over the next five years but in return, the company has to reduce the storm sewage which flows into rivers and the sea.
The announcement on Wednesday 19th December 2024 is the result of a long negotiation process between the water companies in England and Wales and the water sector’s regulator Ofwat. It will see the companies get less than they asked for, but more than Ofwat originally proposed.

Wessex Water completed building the Swanage sewage works at Peveril Point in July 2000
Conditional on delivering investment
Ofwat initially proposed that Wessex Water should cut customers’ bills by two percent over the next five years but the water company argued it needed an increase of 29 percent to deliver the required improvements.
It’s now been told that it can charge 21 percent more. The increase in bills will not be all in one go, but will rise incrementally from 2025 to 2030.
The 21 percent increase is the lowest compared to all the other water companies, although its current average bill is the highest in England and Wales.
However for Wessex Water – and the other water companies – the rise is conditional on delivering its investment programme. If it fails to do so, funding will be subject to a claw back mechanism which will ensure money not spent on investment is returned to customers through lower bills.

Wessex Water has already invested at Swanage sewage works in a new UV light process system which kills bacteria in the water
“We will monitor and hold companies to account”
Across all the water companies in England and Wales, the promised investment programme totals £104 billion.
Ofwat chief executive, David Black said:
“Today marks a significant moment. It provides water companies with an opportunity to regain customers’ trust by using this £104 billion upgrade to turn around their environmental record and improve services to customers.
“Water companies now need to rise to this challenge, customers will rightly expect them to show they can deliver significant improvement over time to justify the increase in bills.
“Alongside the step up in investment, we need to see a transformation in companies’ culture and performance. We will monitor and hold companies to account on their investment programmes and improvements.”

The storm overflow which merges with the Ulwell Stream near Ocean Bay off Shore Road
Wessex Water investment plans 2025 to 2030
As part of the negotiations to increase bills, Wessex Water proposed new investment of £3.65 billion across its region which includes areas of Dorset including Purbeck, Somerset and Bristol as well as most of Wiltshire and parts of Gloucestershire and Hampshire.
Wessex Water says it has committed to upgrade infrastructure, protect the environment, safeguard future water supplies and create local jobs, including:
- £1.13 billion invested to improve water quality by removal of 1,550 tonnes of nutrients in our waterways
- £445 million to reduce the operation of storm overflows. This is more than double the £3 million a month it is currently spending
- Innovative use of sewer monitors to predict problems in the network, real-time water quality monitoring for bathing waters and nature-based treatment solutions including floating reedbeds
- The doubling of investment to create an additional 700 jobs at Wessex Water, with thousands more in the supply chain

The storm overflow at Peveril Point is the most frequently used
Increasingly controversial storm sewage
The biggest issue in Swanage is during periods of high rainfall when the rainwater pours into the combined sewer system. Water companies are legally allowed to use overflow pipes to relieve pressure on sewerage systems, to prevent sewage from flooding homes.
Overflows allow rainwater and diluted sewage (usually screened to remove solids), to bypass sewage treatment works and flow directly into rivers and coastal waters.
While it is allowed, it has become increasingly controversial for the practice to continue, however there are no easy answers as the mainly Victorian drainage system in Swanage was designed to work in that way.
The most used storm overflow in Swanage is at Peveril Point, with the second most used storm overflow at Shore Road near Ocean Bay. There is currently a third storm overflow in Swanage in the middle of the bay but it is hardly ever used to discharge storm sewage.
It is reasonable to expect that Wessex Water’s commitment to reduce the use of storm overflows by 2030, includes those in Swanage.

Wessex Water’s Corfe Castle sewage works is much older and less state of the art than the treatment plant at Swanage

At Corfe Castle sewage works during high rainfall, excess water is collected in this tank, however it can overflow and the untreated sewage diluted by rain water goes into the River Corfe
“Committed to delivering this as affordably as possible”
A Wessex Water spokesperson said:
“We have now received Ofwat’s Final Determination of our Business Plan for 2025-2030, which allows £4.2 billion of expenditure to address a wide range of issues very important to our customers and communities.
“This includes reducing the use of storm overflows, preventing pollution incidents and securing resilient water supplies for the future. The decision contains a lot of detail which we will now be working through.
“We are committed to delivering this as affordably as possible for customers, and this will mean an increase in average bills of around £6 per month next year. We understand that price rises are unwelcome and we will always try to find a way to help customers struggling to pay their bills.”

In 2021 Wessex Water used a helicopter to make improvements to the Ulwell Reservoir which was built in 1930 and supplies drinking water to North Swanage
How Wessex Water compares
Water and wastewater companies
- Wessex Water: 2024/25 average bill £508; 2029/30 average bill £614; up £106 (+21 percent)
- Anglian Water: 2024/25 average bill £491; 2029/30 average bill £631; up £140 (+29 percent)
- Dwr Cymru: 2024/25 average bill £455; 2029/30 average bill £645; up £190 (+42 percent)
- Hafren Dyfrdwy: 2024/25 average bill £392; 2029/30 average bill £557; up £165 (+42 percent)
- Northumbrian Water: 2024/25 average bill £422; 2029/30 average bill £510; up £88 (+21 percent)
- Severn Trent Water: 2024/25 average bill £398; 2029/30 average bill £583; up £185 (+47 percent)
- Southern Water: 2024/25 average bill £420; 2029/30 average bill £642; up £222 (+53 percent)
- South West Water: 2024/25 average bill £497; 2029/30 average bill £610; up £113 (+23 percent)
- Thames Water: 2024/25 average bill £436; 2029/30 average bill £588; up £152 (+35 percent)
- United Utilities: 2024/25 average bill £442; 2029/30 average bill £585; up £143 (+32 percent)
- Yorkshire Water: 2024/25 average bill £430; 2029/30 average bill £607; up £177 (+41 percent)
Water-only companies
- Affinity Water: 2024/25 average bill £192; 2029/30 average bill £241; up £49 (+26 percent)
- Portsmouth Water: 2024/25 average bill £111; 2029/30 average bill £152; up £41 (+37 percent)
- South East Water: 2024/25 average bill £232; 2029/30 average bill £287; up £55 (+24 percent)
Further information
- Ofwat news release about bill increase
- Wessex Water business plan 2025 to 2030
- Bathing water information for Swanage
- More about Swanage sewage works and Corfe Castle sewage works