Since 2020, most storm outfalls in the UK are monitored, so we know a lot more about unplanned sewage discharges into our lakes, rivers and seas. In the North West, are United Utilities getting better or simply making marginal improvements from a really low base?
What’s the issue with storm overflows?
Our sewage system is designed to stop people’s houses being overwhelmed with waste water when there is heavy rain. Ultimately, water must overflow into water courses when the capacity of the sewers and the associated water treatment plants is exceeded. It follows that a well-designed system with sufficient capacity would only overflow under extreme weather conditions.
Sadly, this is not the case in the UK generally and in the North West in particular. Some of the overflows in our region are operating for thousands of hours every year. This means that sewage is bypassing the treatment plants and flowing directly to our regions water courses even in dry weather. These are not ‘storm’ overflows.
Since 2020, the water companies in England and Wales must monitor and report to the Environment Agency on storm overflow discharges (this is known as Event Duration Monitoring or EDM). In April 2023, the figures for 2022 were published.
The companies report only the duration and number of spills – so we do not know the volume, the concentration of sewage, whether any toxins are present or the impact on the water receiving the discharge. However, this outbreak of transparency is clearly a good first step to fixing the problem and it has led to a lot of media coverage. The Liberal Democrats have been pushing the issue during the current local government election campaign.
How are United Utilities doing?
The good news is that the number and duration of storm overflow operations fell between 2021 and 2022, which continues the trend from 2020.


However, one would expect a strong correlation with the amount of rainfall in the North West and in fact this has also fallen over the past three years.

There are tentative signs of progress, although the improvements being delivered have been helped by the weather.
However, the duration and number of spills are still very high. And United Utilities are by some distance the worst performing water company.


United Utilities has 115 overflows that are releasing sewage for more than 1,000 hours per year. The worst, at Plumbland Waste Water Treatment works, near Aspatria in Cumberland did so for nearly 7,000 hours in 2022 – effectively continuously (Environment Agency EDM Returns).

Environment Agency says the situation is “totally unacceptable”
In a blog post accompanying the release of 2022 EDM data, the Environment Agency were very clear on their view of the situation.
“The 2022 EDM data shows a decrease in spills, which reflects last year’s drier than average weather. Despite claims by water companies and Water UK, the body that represents their interests, there is no evidence to show it is because of water company action. In fact, last year water companies only made improvements to 65 storm overflows – less than 0.5% of the overall total of overflows in the entire system – so we are very confident that water company action has not significantly contributed to the reduction in flows overall. For them to claim otherwise is wilfully misleading.”
“What is very clear from the data they have provided is that the number of spills they are allowing on the sewerage network is far too high and totally unacceptable. We are considering whether any action is required under our Enforcement and Sanctions Policy.”
United Utilities have a plan
United Utilities have responded to Environment Agency, media and political pressure on this issue. They have published the first version of a plan for storm discharges. It outlines a 4-step improvement plan:
- Ensuring our operations progressively reduce impact to river health.
- Being open and transparent about our performance and our plans.
- Making rivers beautiful and supporting others to improve and care for them.
- Creating more opportunities for everyone to enjoy rivers and waterways.
Some investments are being made and there is clearly more focus on this as an issue (new teams are being set up and work on data analysis is being emphasized).
But Louise Beardmore, the new CEO, sounds a note of caution:
“But in the same way we can’t introduce Electric Vehicle charging overnight, nor can we re-plumb the North West drainage network that was built over the last 150 years in a handful of years. In our region, over half of the sewer network is combined – this means that when it rains, rainwater joins sewage and the sewer fills up quickly. In Liverpool, 84% of the sewers are combined.”
Where do we go from here?

It’s clear that decades of underinvestment cannot be corrected overnight and that up to £600bn according to the government’s taskforce will ultimately be needed to eliminate the problems we have (by separating waste water and rain water into separate systems). Any plan must start with recognising the true scale of the problem and then stop the problem getting worse. This means ensuring that new developments are constructed to higher standards and initially at least focussing on the worst performing outflows.
It is within the Government’s power to ensure that more money is ploughed into storm overflow improvements rather than being paid out in dividends to overseas shareholders – cumulatively £65bn since privatisation. The current financial model for the water industry is probably not the right one to handle the demand, which will lead to conflict in future years. Perhaps our much vaunted financial services industry can create funding solutions and deliver some socially useful outcomes.
Storm discharges are only one of many pressures on our water courses – agricultural pollution caused by runoff of chemicals used in farming is arguably a bigger problem. We need to be careful to prioritise investment so we get the best outcomes.
United Utilities, with an old infrastructure and higher than average rainfall has more of a problem than other water companies. How will the people of the North West feel about paying higher water bills than other UK citizens for a worse outcome?