--- title: Ofwat’s New Trunk Main Leakage Rules description: Discover the challenges and innovations in meeting Ofwat's new trunk main leakage rules and how to achieve proactive, data-driven leakage management. image: https://www.crowderconsult.com/hubfs/Ofwats-New-Trunk-Main-Leakage-Rules-Challenges-And-Innovative-Solutions.png --- [![Crowder Consulting Logo](https://www.crowderconsult.com/hs-fs/hubfs/Crowder%20Consulting%20Logo.png?width=253&height=226&name=Crowder%20Consulting%20Logo.png "Crowder Consulting Logo")](https://www.crowderconsult.com/) - [0151 647 7772](tel:0151%20647%207772) - [enquiries@crowderconsult.co.uk](mailto:enquiries@crowderconsult.co.uk) - About - [Mission & Vision](https://www.crowderconsult.com/mission-vision) - [Management Team](https://www.crowderconsult.com/management-team) - [Contact Us](https://www.crowderconsult.com/contact-us) - [Blog & News](https://www.crowderconsult.com/blog) - [Testimonials](https://www.crowderconsult.com/testimonials) - [Careers](https://www.crowderconsult.com/careers) - [Case Studies](https://www.crowderconsult.com/case-studies) - Netbase & Digital Services - [Netbase Water Network Management System](https://www.crowderconsult.com/netbase-water-network-management-system) - [Netbase Digital Services Platform](https://www.crowderconsult.com/netbase-digital-services-platform) - [NetOps - Smart Water Network Application](https://www.crowderconsult.com/netops-smart-water-network-application) - [NetAlytics - Smart Advanced Water Network Analytics](https://www.crowderconsult.com/netalytics-smart-advanced-water-network-analytics) - [View All Services](https://www.crowderconsult.com/netbase-digital-services-solutions) - Consultancy - [Leakage Management in District Areas (DMAs)](https://www.crowderconsult.com/leakage-management-in-district-areas) - [Non Revenue Water Reduction Programmes](https://www.crowderconsult.com/non-revenue-water-reduction-programmes) - [Upstream Water Network / Trunk Mains](https://www.crowderconsult.com/upstream-water-network) - [Hydraulic Modelling of water networks](https://www.crowderconsult.com/hydraulic-modelling-of-water-networks) - [Pressure Reduction & Optimisation](https://www.crowderconsult.com/pressure-reduction-and-optimisation) - [Specialist network studies and analyses](https://www.crowderconsult.com/specialist-network-studies-and-analyses) - [View All Services](https://www.crowderconsult.com/consultancy-services) - Data & Data Science - [Tactical Smart Meter Data Solutions](https://www.crowderconsult.com/tactical-smart-meter-data-solutions) - [Connecting to Corporate & Cloud Systems Data](https://www.crowderconsult.com/connecting-to-corporate-and-cloud-systems-data) - [Data validation and visualisation](https://www.crowderconsult.com/data-validation-and-visualisation) - [View All Services](https://www.crowderconsult.com/data-science-services) - Field/Leakage - [Leakage Detection](https://www.crowderconsult.com/leakage-detection) - [Trunk mains investigations and leakage surveys](https://www.crowderconsult.com/trunk-mains-investigations-and-leakage-surveys) - [Hydraulic Modelling Field Tests](https://www.crowderconsult.com/hydraulic-modelling-field-tests) - [DMA Sectorisation](https://www.crowderconsult.com/dma-sectorisation) - [Meter Verification Surveys](https://www.crowderconsult.com/meter-verification-surveys) - [Water Efficiency initiatives](https://www.crowderconsult.com/water-efficiency-initiatives) - [View All Services](https://www.crowderconsult.com/field-leakage-services) - Training - [Water Network Management](https://www.crowderconsult.com/water-network-management) - [Production Planning](https://www.crowderconsult.com/production-planning) - [Leak Detection](https://www.crowderconsult.com/leak-detection) - [Netbase](https://www.crowderconsult.com/netbase) - [National Water Hygiene Card & SHEA Water](https://www.crowderconsult.com/national-water-hygiene-card-shea-water) - [NetOps Training](https://www.crowderconsult.com/netops-training) - [View All Services](https://www.crowderconsult.com/training) # Ofwat’s New Trunk Main Leakage Rules – Challenges and Innovative Solutions 24 June 2025 ## Changing Regulations and New Expectations The UK water regulator, Ofwat, has introduced important new requirements for how water companies measure and manage leakage on trunk mains. Under the latest guidance tied to PR24 performance commitments, water companies must significantly change their approach to [trunk main leakage](https://www.crowderconsult.com/trunk-mains-investigations-and-leakage-surveys). Key changes include: [![CONTACT US](https://hubspot-no-cache-eu1-prod.s3.amazonaws.com/cta/default/143230470/interactive-110125449659.png)](https://www.crowderconsult.com/hs/cta/wi/redirect?encryptedPayload=AVxigLLBGN%2BWYCqqefKx1mAS3aXi8cANgYv%2FRwN0hdriRdPLDMOa3bMnXTDPSruklSETwxMA3bsGyo2aj3RU0xkt9RoLFFtXO6vOhsZ3oBV0%2Fm4BqY9jAiypaiUnQ5ynHzoUw3N0qKiyZJAfEu5agin3b4IyVy3iPTq2WbHGA10xtpNQ6p7ZmBVrcDXL9i8UD0WsNWHEMEj0N27HYQeOXnICtsPJ&webInteractiveContentId=110125449659&portalId=143230470) - ### New measurement method: Phasing out the old Bursts And Background Estimate (BABE) calculation method, previously a default for trunk mains leakage, in favour of a flow balance approach as the standard for monitoring trunk main losses. - ### Data accountability: Requiring companies to rely only on their own measured data to estimate trunk main leakage (no generic industry assumptions). Companies also have to report the total length of their trunk mains asset base to Ofwat by May 2025, underscoring the need for better trunk network inventory and data. - ### Heightened scrutiny: Mandating an annual review of leakage figures if trunk main leakage exceeds 5% of the company’s total leakage. In other words, if a significant share of overall leakage is coming from trunk mains, it must be revisited and validated each year. - ### Proactive monitoring trigger: If trunk main losses form a significant element (\>5%) of total leakage (or the MLE water balance gap is more than ±2%), the company must implement a proactive trunk main leakage monitoring approach. This proactive approach can mix flow balances, field inspections, analytical, and innovative techniques to actively find and fix leaks. These new expectations are driving a more hands-on, data-driven strategy for trunk mains. Ofwat’s message is clear: large transmission pipelines can no longer be a “blind spot” in leakage management. Utilities must know how much their trunk mains are leaking and take action if it’s substantial. This represents a shift from past practices and poses new challenges in practice. ![Close-up view of a blue trunk water main pipe junction partially buried in soil, illustrating critical infrastructure at risk of leakage, relevant to Ofwat's updated regulatory focus on trunk main leakage detection, monitoring, and repair innovations.](https://www.crowderconsult.com/hs-fs/hubfs/Ofwats-New-Trunk-Main-Leakage-Rules-Challenges-And-Innovative-Solutions.png?width=1100&height=750&name=Ofwats-New-Trunk-Main-Leakage-Rules-Challenges-And-Innovative-Solutions.png) ## Why Trunk Main Leaks Are Hard to Detect Meeting these requirements is easier said than done. Trunk mains, which are the big arteries of the water network that carry water from treatment works to distribution areas, have historically been difficult to monitor and often received less attention in leakage programs. There are several reasons why [detecting leaks on trunk mains](https://www.crowderconsult.com/blog/improving-and-maintaining-water-network-efficiency) is uniquely challenging: - ### Limited instrumentation: Unlike distribution networks (often split into DMAs with meters on every boundary), trunk mains historically have few flow meters along their length. Implementing Ofwat’s flow-balance method presupposes having inlet/outlet meter data, yet many trunk mains lack permanent metering. Retrofitting large pipelines with meters or flow sensors is costly and logistically complex. - ### Sheer scale: Water companies typically oversee thousands of miles of trunk pipelines. Expecting to physically inspect or patrol every mile regularly is impractical. Simply walking the line of each trunk main to check for leaks, even just once a year, would consume enormous time and resources. - ### Fewer visible clues: Trunk mains are often buried deep underground and carry water at high pressure over long distances. When they leak, the water may not visibly surface for a long time (if at all) because of depth and pressure dissipation. These leaks can run silently for years without obvious above-ground signs. The absence of telltale puddles or pressure drops means a trunk main could be leaking large volumes unnoticed until a major burst occurs. - ### Higher consequences, higher cost: Ironically, when a trunk main leak does become apparent, it’s usually because it has grown into a major burst, which can flood streets and disrupt service to large areas. By that stage, the volume lost is massive, since trunk mains carry huge flow rates. Yet proactively searching for minor leaks along big pipes is expensive and technically difficult, leading many utilities in the past to focus on easier wins in the distribution network. Traditional acoustic [leak detection](https://www.crowderconsult.com/blog/technologies-for-water-leakage-detection) methods (like listening with ground microphones or simple correlators) are labour-intensive on long trunk lines with few access points. In short, trunk mains historically suffered from an “out-of-sight, out-of-mind” problem in leakage management. Given these challenges, it’s understandable why the new Ofwat rules create some anxiety for water companies. How can they practically achieve regular monitoring of trunk mains, detect leaks early, and meet the tougher reporting standards? The answer lies in leveraging a combination of data analytics and targeted new technologies to overcome the limitations of traditional methods. ## Adapting to Changing Regulations: Take Control of Your Trunk Mains The new Ofwat regulations demand a proactive, data-driven approach to [trunk main leakage](https://www.crowderconsult.com/trunk-mains-investigations-and-leakage-surveys). Contact us today to learn how our solutions can help you navigate the changing regulatory landscape and achieve your leakage reduction goals. 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