Imagine glancing at your phone on a drizzly morning in Devon or Cornwall and seeing a storm overflow alert for the stretch of coast where you planned to swim, surf, or take the dog for a walk. Your heart sinks a little. You picture untreated water reaching the sea, and you wonder whether it’s safe. That is exactly the kind of scenario South West Water is trying to address with a recent explanation about its WaterFit Live web page. The company has noticed that, from time to time, an alert appears on the page even though no actual storm overflow spill has occurred. For most people, an alert is an alert — it means something has gone wrong. But South West Water wants to help customers understand why that is not always the case. The company has been investigating a number of alerts that were later confirmed not to have been caused by storm overflow activity. Helen Dobby, Head of Environmental Performance at South West Water, put it plainly: people naturally assume that an alert means a spill has taken place. In the vast majority of cases, that is exactly what it means. But occasionally, after investigation, the company finds the alert was triggered by something entirely different. It is a bit like a home security system going off when a tree branch brushes against a window – the alarm is real, but there is no intruder. The message here is not that alerts should be ignored, but that the technology behind them is not infallible. South West Water is trying to balance the need for speed with the need for accuracy, and that balancing act is more complicated than many people realise.
The story begins with the sensors that make WaterFit Live possible. Storm overflow alerts on the website are generated by devices called Event Duration Monitors, or EDMs. These sensors are installed at storm overflow locations, which are designed to operate during periods of heavy rainfall. Storm overflows themselves are not necessarily a sign of neglect; they are part of a sewerage system that allows excess water to escape when the network would otherwise be overwhelmed. In an ideal world, they would never operate, but in a wet climate with ageing infrastructure, they sometimes do. The EDM’s job is to detect when a spill starts and when it stops, and to send that information back to South West Water so the public can see it in near real time. For most of the time, these monitors work correctly, and the alerts they produce reflect genuine activity. That is why South West Water publishes them so openly: people who care about water quality have a right to know what is happening in their local rivers and seas. But EDMs are physical devices sitting in harsh environments, surrounded by mud, leaves, stones, and all the other debris that flows through sewer systems. They can be knocked out of alignment, blocked, or damaged. Sometimes the sensors are fine, but the telemetry systems that transmit their signals fail, producing confusing or incorrect information. The result is a false alert: a warning appears on WaterFit Live, but when engineers investigate, they find that no spill ever happened. The system is doing its best, but it is not perfect, and the difference between a real alert and a false one can take time to untangle.
False alerts can be caused by a variety of everyday problems. Debris might pass over the sensor and trigger it, or an obstruction might interfere with the way the monitor measures water flow. Faults can also develop in the sensor itself, or in the communication equipment that sends data from the overflow site back to the company’s systems. These issues are not always easy to diagnose. Sometimes a monitor sends a signal that looks perfectly valid, and only after a careful check on site does the truth emerge. South West Water recently dealt with exactly this situation in Falmouth. An alert appeared on WaterFit Live, and the company investigated it thoroughly. In the end, they confirmed that the alert was false. The EDM in question was faulty. Once that was discovered, the company took steps to suppress any further non-genuine alerts from that monitor until the problem could be resolved. This is important context. It would be easy to look at a false alert and conclude that the company is hiding something, but the opposite is true: the very fact that the company can identify and correct false alerts shows that it is actively monitoring its monitoring equipment. Helen Dobby emphasised that the company wants customers to have the most accurate and up-to-date information possible. When investigations show that a spill has not taken place, WaterFit Live is updated, and steps are taken to prevent further incorrect alerts while the issue is being sorted out. No one likes to see a warning that turns out to be wrong, especially when it relates to something as sensitive as water quality, but the company’s willingness to explain and correct these mistakes is part of the larger effort to be transparent.
South West Water publishes storm overflow alerts in near real time because it believes that water users should have access to information as quickly as possible. That is a commendable principle, but it comes with a trade-off. When information is released instantly, it has not always passed through every available check. In most cases, speed and accuracy align, but in a small number of cases, further investigation shows that the alert was not caused by a real spill. Helen Dobby acknowledged this directly, noting that in a small number of cases, an alert may appear before all checks have been completed, and later checks may reveal that no spill actually took place. The company also shares its monitoring data with external organisations, including Surfers Against Sewage, which uses the information in its Safer Seas & Rivers Service. This is part of a broader ecosystem of water quality information. Alerts are shared at the earliest opportunity, and any corrections are passed on once investigations are complete. However, because different platforms process updates at different times, the information displayed on WaterFit Live and on third-party services may occasionally vary. One app might show an alert while another has already removed it, or vice versa. That variation can be confusing, but it is a natural consequence of sharing data openly and quickly. South West Water is not trying to hide anything by pointing out these discrepancies; rather, it is trying to help people understand the difference between a genuine alert, a false alert, and a correction that has yet to appear on every screen. The goal is to build trust, and building trust means explaining the imperfections in the system as well as celebrating its successes.
Behind all of this is a substantial maintenance effort. South West Water says it minimises the risk of false alerts through regular maintenance and calibration of its monitoring equipment. That is not a vague promise; the company currently reports that its EDM operability is 96.7 per cent across 1,361 storm overflows. That figure is the second highest in the industry and well above the national average. In other words, the vast majority of monitors are working as they should, most of the time. The remaining 3.3 per cent might sound small, but when you have more than 1,300 monitors, even a small percentage represents a significant number of potential faults. South West Water is continuing to invest in improvements, including additional sensors and upgrades to its IT systems, to help identify false alerts more quickly. This is not just about fixing broken equipment; it is about creating a smarter system that can tell the difference between real events and false signals. Helen Dobby said the company recognises that false alerts can be confusing for customers, which is why it is continuing to invest in monitoring equipment, sensors, and technology to help identify and correct them as quickly as possible. There is a genuine human concern behind these technical fixes. People plan their days around water quality. Parents paddle with their children in shallow bays, surfers rely on wave forecasts, and local businesses depend on tourism. A false alert is more than a minor inconvenience; it can change plans for the day, damage confidence in local water quality, and cast doubt on the very system that is supposed to keep people informed. South West Water seems to understand that a single false alarm can undermine months of trust-building, and that is why the response matters as much as the initial alert.
Ultimately, this is a story about the messy, imperfect reality of trying to be transparent about environmental monitoring. South West Water is not claiming that its system is flawless. It is saying that the alarms can sometimes be wrong, and that when they are wrong, the company will investigate, correct the record, and improve the hardware and software that made the mistake possible. That is a more honest position than pretending every alert is perfect. For water users, the takeaway is not to stop paying attention to alerts, but to understand what they are and what they are not. An alert on WaterFit Live is the beginning of a conversation, not always the final word. It invites you to check for updates, to understand that monitoring is a living, ever-improving process, and to recognise that the people running the system are working hard to keep false alarms to a minimum. The company’s decision to explain all of this openly is itself a sign of progress. Instead of hiding behind jargon, South West Water is talking to customers in plain language about sensors, debris, telemetry faults, and the careful work of investigation. In the long run, that kind of honesty is what builds confidence. People still want cleaner rivers and seas, and there is still much work to do, but understanding how the monitoring system works is an essential part of the journey. The next time an alert appears and later turns out to be false, it will still be frustrating — but at least we will know that someone is watching over the monitors, checking the warnings, and doing everything they can to make sure that when the alarm rings, it is for a real reason, not a ghost in the machine.