The landscape of water management is shifting, especially with new regulatory pressures on trunk main leakage. Fortunately, the industry's toolkit for leak detection has advanced beyond manual acoustic surveys. Recent technological developments enable leaks to be detected far more efficiently and accurately than in the past. To meet Ofwat's requirements and effectively manage trunk main leakage, water companies are now adopting a multi-pronged strategy.
This includes a smarter use of data and innovative detection techniques, with key components such as:
Flow Balance Analytics:
At the core of the new approach is the use of flow data analytics to quantify losses on trunk mains. This involves installing and validating flow meters at strategic points – for example, at water treatment works outputs, reservoir inlet/outlets, and at key nodes feeding distribution zones. By comparing the volume of water entering a trunk main section with the volume delivered out (after adjusting for known consumption), any unexplained discrepancy is flagged as potential leakage. This flow-balancing can operate continuously or through periodic measurements, serving as a “leak alarm” for trunk mains. It turns a previously invisible problem into a measurable water balance. Ofwat’s shift to a flow balance methodology essentially forces the implementation of these analytics, but it also gives companies better insight into where losses are occurring.
Trunk Main Area (TMA) Sub-division:
Because trunk networks are so extensive, a single balance for the entire system isn’t always actionable. The solution is to sub-divide the trunk mains into logical Trunk Main Areas (TMAs), analogous to District Meter Areas (DMAs) in the distribution system. Each TMA is a section of the upstream network with defined boundaries (usually isolation valves or breakpoints) and dedicated metering of inflows/outflows. Creating TMAs often requires verifying network connectivity (ensuring valves that should be closed are indeed closed, and mapping any cross-connections) and installing new meters or pressure/flow sensors at key locations. Once in place, each trunk main area can be monitored for leakage as a unit. Additionally, where required, further subdivision can be implemented to sectorise zones within a TMA. This granular approach means that if one trunk area shows an anomalous loss, the problem is isolated to that zone rather than having to search the entire network. TMAs effectively break a huge task into manageable chunks and improve the resolution of leak detection efforts.
Targeted Acoustic Correlation Surveys:
Even with flow analytics pinpointing a suspicious trunk main section, you still need to find the exact leak location on the ground. Traditional acoustic leak detection (listening for leak noise with microphones) is tricky on large pipes, but advanced tools have greatly improved its effectiveness. One such method is acoustic correlation using sensors placed at multiple points along a pipe. By recording the leak noise and analysing the time it takes for sound to reach each sensor, correlators can calculate the leak position with high accuracy. Modern correlators designed for trunk mains use highly sensitive hydrophone sensors (often placed via hydrants or fittings) and cloud-based analysis to filter out interference. They can cover longer distances than older devices, which is crucial for big mains. Instead of blanketing an entire city with sensors, utilities can now deploy correlators in a targeted manner – for example, along a 5 km stretch of a trunk main that flow data indicates is losing water. This focused use of acoustic technology allows field teams to efficiently locate the leak sound and pinpoint the leak for repair. It’s a far more efficient approach than randomly listening to every pipe, and it has been proven effective: in one case, a utility surveyed over 10,000 km of trunk mains in a few years using correlators and found hundreds of leaks, saving tens of millions of litres of water per day.
Other Innovative Tools:
Beyond acoustic methods, there exist numerous other technologies that can assist in locating leaks on trunk mains. Some notable options available include (but are not limited to) satellite leak detection, in-pipe solutions with cameras and microphones, and sonar.
Each of these techniques, on its own, provides part of the solution. Combined in a coherent strategy, they complement each other. Flow analytics and TMA segmentation tell you which area to investigate; acoustic correlation and other innovative solutions tell you where within that area the leak is likely to be. This layered approach is exactly what Ofwat envisions with its call for a mix of methods (analytical, field, innovative), it’s about using data to drive smart detection efforts, rather than either purely guessing or purely brute-forcing with field crews. Ultimately, these modern methods allow utilities to find trunk main leaks much earlier and more efficiently than before, helping to reduce water loss and prevent those headline-grabbing burst incidents.
Crowder’s NetConn Process: An End-to-End Solution
One example of this new mindset in action is Crowder Consulting’s “NetConn” process for trunk mains leakage management. Crowder has developed a robust, end-to-end methodology that ties together data analysis, field investigation, and continuous improvement, exactly the kind of holistic approach needed to tackle trunk main leakage under the new regulations. In practice, Crowder’s approach works as follows:
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Network data verification:
The process begins by establishing an accurate picture of the trunk main network. This means ensuring all sources, valves, and meters are accounted for (often uncovering unknown cross-connections or fixing incorrect schematic data). Crowder’s team uses tools like their proprietary Netbase system and water network schematics to map out trunk main areas and check boundary integrity. Meter accuracy and availability is also scrutinised and where required, validation exercises such as secondary location verifications are undertaken by Crowder field team engineers. By validating meter availability and accuracy, and the operational status of valves, they make sure that each trunk main area is properly isolated for monitoring. This “network connectivity” step is critical, without trustworthy data, any flow balance calculation could be misleading.
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Analytical monitoring and targeting:
With the trunk main areas defined, Crowder applies continuous meter and demand balance analysis on each area. Their analysts leverage advanced software to monitor flows, pressures, and nightline usage in the upstream network. The result is a dashboard of performance indicators for each trunk zone ( the NetAlytics platform), essentially health scores that highlight unusual losses or inefficiencies and priority TMAs to focus on investigating/resolving. When the data shows that a particular area has a higher-than-expected loss (relative to input flow), it is flagged for investigation. This kind of data-driven targeting allows Crowder to prioritise which trunk mains likely have leaks and avoid wasting effort on sections that are tight. The analysis-to-action translation is a key strength of the NetConn methodology: it turns numbers into an actionable leak targeting plan.
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Field leak detection and repair:
Next, Crowder’s field teams move in with targeted leak detection surveys on the respective trunk main sections. Depending on the scenario, they might deploy acoustic correlators, noise loggers, or even conduct a satellite scan in partnership with technology providers. For example, Crowder’s specialists use high-spec multi-point correlation equipment with hydrophone sensors to listen for leak noise on large diameter mains. These advanced correlators can pinpoint a leak’s location along a trunk main, even if the leak is too small to be noticed otherwise. By focusing only on the trunk areas identified by the analytics, the field crews work efficiently, often confirming a leak and pinpointing its exact site for repair in a fraction of the time a random sweep would take. Once the leak is located, the water utilities repair crews excavate and fix it, restoring the integrity of the main.
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Continuous improvement cycle:
What sets the NetConn process apart is that it doesn’t end with one find-and-fix exercise. It is a cyclical, continuous improvement loop. After repairs, the trunk main area’s flow balance is measured again to verify that leakage has dropped, confirming the success and quantifying the savings (where possible). The network data is then updated (for instance, noting the new baseline flow, any changes in pressure management, etc.), and the cycle of monitoring continues. Over time, this systematic approach tightens up the whole trunk network. By regularly monitoring trunk main areas, maintaining meters and boundaries, and swiftly addressing any new inefficiencies, Crowder’s methodology ensures that trunk mains remain under close control. Essentially, it provides a sustainable way to manage trunk main leakage as an ongoing operational task, rather than a one-off project. This end-to-end approach, from initial data gathering to final repair and feedback, exemplifies industry best practice in the PR24 era. It gives water companies a clear roadmap to comply with Ofwat’s requirements while also delivering real-world reductions in water loss and risk.
Notably, while Crowder’s NetConn process is a specific example, the principles behind it are broadly applicable. It shows that with the right combination of accurate data, analytics, and field expertise, utilities can indeed conquer the trunk mains leakage challenge. What was once deemed “too hard to find” is now being actively tracked down and repaired. The subtle but important outcome is a shift in culture, trunk mains are no longer neglected assets, but a core part of the leakage management program.
Conclusion: Turning Obligation into Opportunity
Ofwat’s heightened focus on trunk main leakage has certainly raised the bar for UK water companies. Utilities can no longer rely on rough estimates or hope that big leaks will simply reveal themselves. The new rules compel companies to know their trunk mains intimately, measuring their performance and acting quickly when things go wrong. This might seem like a compliance burden at first, but in truth it’s an opportunity to modernise how we manage critical water infrastructure. By embracing data-driven techniques like flow balancing and trunk main zoning, and by deploying cutting-edge detection tools such as acoustic correlators and other innovative solutions, water companies can dramatically improve their ability to find and fix leaks that were previously invisible.
The benefits go well beyond satisfying the regulator. Reducing trunk main leakage conserves valuable water resources, improves supply reliability for customers, and can prevent catastrophic main bursts by catching leaks early. It also pushes the industry toward a more proactive and intelligent operational model.
In the coming years, we can expect to see many utilities adopting similar holistic strategies, supported by consultants and technology partners, to meet the Ofwat requirements. Those that do will likely not only hit their regulatory targets but also reap the rewards of lower water loss and improved network resilience. In summary, trunk mains leakage is no longer the “forgotten” part of the water network, it’s front and centre. With a clear mandate and an array of modern solutions at hand, the industry is set to make trunk main leaks a problem that can be solved, rather than just estimated. This marks a positive step toward a more efficient, sustainable water supply system for everyone.
Find Out More On Data-Driven Trunk Mains Investigations And Leakage Surveys
Ready to proactively manage your trunk mains and achieve your leakage reduction targets? Discover how Crowder's NetConn process, an end-to-end solution for data-driven trunk mains investigations and leakage surveys, can transform your approach to water loss.
