As part of our commitment to transparency, we share storm overflow data in several different ways. Firstly, it’s available through WaterFit Live on our website. We also share data with the National Storm Overflow Hub so they can present it on their website. We also share data with third parties such as Surfers Against Sewage (SAS) and MyCoast.
We are delivering a plan to reduce reliance on storm overflows, which will help to improve water quality in rivers and the sea, especially bathing waters. Alongside this work, we provide data about storm overflow operation so people can make informed decisions about when to enter the water.
We value relationships with stakeholders including environmental groups and organisations, who can provide insights and perspectives that help to inform our work. Sharing our data in these ways is an important part of this commitment.
Storm overflows are pressure relief valves that release excess wastewater when the network is overwhelmed, typically after heavy rainfall. Without storm overflows, waste could back up and spill into homes and businesses.
Learn more about storm overflows.
WaterFit Live provides near real-time data about our storm overflows, and whether they are potentially impacting water quality at particular designated bathing waters.
You can also learn more about how we're investing in your area to reduce the need for storm overflows to operate.
You can access this information via our WaterFit Live maps:
It does not identify impacts from other sources, such as agricultural and urban run off.
Event Duration Monitors (EDM)s measure whether the overflow is active and for how long. They don’t show the volume of wastewater that spills from an overflow. This means an alert is triggered to show an overflow is active even if the volume of wastewater being spilled is very low. They can also be triggered by small objects like twigs or spider webs, producing a false positive activation.
The data is also published in reports on a monthly basis, with publication by the last Friday of the following month. For example, on the last Friday of January 2025, EDM start/stop data will be published showing data up to 31st December 2024.
You can also find our annual EDM Return published on our website.
In November 2024 the National Storm Overflow Hub went live with South West Water data along with all other Water and Sewerage Companies (WASC) data. This is open to the public and available for 3rd party use. An example of 3rd party use is the National Rivers Trust who have already used it to create their own map.
The National Storm Overflow Hub receives the same activation and deactivation data that is used on WaterFit Live. They also receive our Storm Overflow Action Plan (SOAP) from the Department for Environment, Food and Rural Affairs (DEFRA). This includes asset details, what kind of interventions may be put in place, completion dates and investment details. This same information is shared on our WaterFit Live maps.
We engage with multiple organisations to share alerts about the potential for impact on a designated bathing water, should one of our storm overflows be activated. Our alert system sends notifications to the relevant organisations and buisnesses.
These external recipients include, beach managers, councils, environmental groups, holiday resorts and hotels. They will receive alerts based on proximity to a bathing water.
For example, SAS and MyCoast receive alerts for all bathing waters that may be impacted by our storm overflows. Whereas some organisations receive just one alert about a specific bathing water close to them.
Both SAS and MyCoast receive the same notifications. How they use the data is different and is not controlled by South West Water.
The alerts sent contain the same information that we share on our bathing water quality map.
Watch our video explaining how storm overflows work.
Understand how rainfall affects water quality.