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. Key changes include:
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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.
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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.
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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.
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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.
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 is uniquely challenging:
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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.
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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.
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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.
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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 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.
Add image of trunk main (in red) with DMAs protruding from it.
Figure 1 - Trunk mains often span large distances across urban and rural areas (highlighted in red on the map). Leaks on these large pipelines may not be obvious on the surface, making proactive detection methods crucial.
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. Contact us today to learn how our solutions can help you navigate the changing regulatory landscape and achieve your leakage reduction goals.
