Improved inflow and infiltration outcomes at Anglian Water through network analytics
Excess inflow and infiltration are a major source of pollution risk and operational cost across wastewater networks. In partnership with Stormharvester, Anglian Water adopted a data-driven approach to understand the true scale of the problem, validate root causes, and target investment. The result was measurable performance improvement and a more confident, evidence-led approach to I&I management.
Inflow and infiltration (I&I) are among the most persistent and complex challenges facing wastewater utilities. Excess water entering foul sewer networks, whether through misconnected surface drainage, groundwater usually infiltrating through cracks, damaged open joints, or manholes, creating excess “clear water” entering the foul sewer network , or fluvial influences, can overwhelm system capacity, drive up operational costs, and increase the risk of pollution incidents.
Inflow and infiltration are key challenges, with excess water overwhelming sewer capacity, driving up costs and increasing pollution risk
For Anglian Water, hydraulic overloading caused by I&I is not an abstract problem. During AMP7 (2020–2025), it was a contributing factor in nearly a quarter of pollution events across the company’s wastewater network. With climate change intensifying rainfall patterns and regulatory scrutiny increasing, the need to better understand, prioritise, and mitigate I&I has become critical.
Against this backdrop, Anglian Water partnered with Stormharvester to take a fundamentally different approach, one rooted in advanced analytics, continuous monitoring, and evidence-led decision-making. The result was a data-driven intervention that delivered a 20% reduction in I&I-related flows, saved almost 600 hours of pumping station runtime, and directly informed £2.4 million of targeted investment. This case study demonstrates how turning network data into actionable intelligence can transform how utilities tackle one of wastewater’s most entrenched problems.
The challenge: moving beyond assumptions in an I&I hotspot
During AMP7, hydraulic overloading caused by I&I contributed to nearly a quarter of pollution events across Anglian Water’s network
I&I rarely originates from a single cause. Instead, it is typically the result of multiple overlapping mechanisms, including surface water ingress from highways, groundwater infiltration through cracks, damaged open joints, or manholes, creating excess “clear water” entering the foul sewer network, misconnections from properties and paved areas, and fluvial flooding from nearby watercourses. Each source behaves differently and requires a tailored response.
Within Anglian Water’s network, one particular catchment had been an ongoing focus due to repeated pollution events and operational stress at a downstream sewage pumping station. While engineers had developed working theories about where excess water was entering the system, confirming those assumptions proved challenging.
Traditional investigation methods, such as CCTV surveys, dye testing, and physical inspections, were expensive, time-consuming, and often inconclusive. They provided snapshots in time rather than a continuous picture of network behaviour, making it difficult to capture peak infiltration events that typically occur during specific seasonal or weather conditions.
Anglian Water identified three critical needs: to validate assumptions about suspected sources of inflow and infiltration, to sense check findings in order to distinguish true root causes from coincidental correlations, and to prioritise interventions using accurate, actionable data rather than intuition. Meeting these needs required a step change in visibility, one that could reveal not just where problems existed, but how they evolved over time and under varying hydraulic conditions.
The approach: advanced analytics for a holistic network view
To address this challenge, Anglian Water deployed Stormharvester’s inflow and infiltration detection technology across the hotspot area. The objective was to gain a holistic, system-wide understanding of wastewater network behaviour by combining existing sensor data with advanced analytics.
Stormharvester’s platform ingests high-frequency data from sewer level monitors, pumping stations, and rainfall sources, applying proprietary analytics to differentiate between dry weather flow, infiltration, and rainfall-driven inflow. By learning baseline network behaviour, the system can automatically flag anomalies and quantify the volume, timing, and likely origin of excess water entering the system.
Anglian Water partnered with Stormharvester on a data-driven approach rooted in advanced analytics and evidence-led decision making
This data driven approach enabled several key capabilities, including rapid validation of root causes that allowed suspected problem areas to be confirmed or ruled out using objective evidence, targeted investigations that directed field teams to the right assets at the most critical times of the year, and network wide hotspot identification that revealed clusters of infiltration and inflow which may not have been visible through conventional methods.
Crucially, the analytics moved beyond simple alarm thresholds. By contextualising flow patterns against rainfall and seasonal groundwater levels, Anglian Water could distinguish between normal wet-weather responses and abnormal ingress that warranted intervention. What emerged was a far clearer picture of how, when, and where I&I was impacting the network, and how those impacts translated into downstream operational stress.
Results: quantifying the true scale of the problem
The analysis revealed the true scale and nature of hydraulic overloading in the catchment. Stormharvester’s platform detected more than 1,000 individual instances of groundwater infiltration, highlighting widespread asset-level vulnerabilities that had previously gone unquantified. In parallel, the system identified 303 inflow connections, equivalent to approximately 60,000 square metres of connected surface area entering the foul sewer network.
To put this into context, the additional water entering the system was equivalent to nearly seven Olympic-sized swimming pools, a volume more than sufficient to overwhelm downstream infrastructure during wet weather.
Armed with this intelligence, Anglian Water was able to move decisively. The outputs from the analysis directly informed £2.4 million of targeted interventions, scheduled for delivery within the current and next AMP periods. Rather than blanket rehabilitation or reactive maintenance, investment could be focused precisely where it would deliver the greatest hydraulic and environmental benefit.
Measured impact: from insight to operational performance
Performance improvements were tracked across two consecutive winter periods, allowing Anglian Water to compare conditions before and after mitigation actions were implemented. The results were clear, with a 20% total reduction in flow attributed to ingress, inflow and infiltration, alongside almost 600 hours less pumping station runtime, delivering significant energy and operational savings.
Manhole level data illustrated a marked reduction in peak flow events following intervention. Before action, monitored manholes regularly experienced sharp level spikes during rainfall, indicating rapid inflow and infiltration. After targeted remediation, these spikes were significantly reduced, demonstrating improved system resilience under wet-weather conditions.
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Manhole level data. Image shows the levels on flow in the system prior to the implementation of StormHarvester.
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Manhole level data. Image shows the improvement after action taken by Anglian Water as a result of the insights provided by StormHarvester.
Similarly, analysis of sewage pumping station runtime data showed a substantial reduction in pump operation associated with infiltration and inflow. The breakdown of runtime by flow type confirmed that the reduction was not due to lower demand, but to the successful removal of excess water from the network.
These improvements translated into tangible operational benefits: reduced wear on mechanical assets, lower energy consumption, and increased hydraulic headroom during storm events.
The intervention delivered a 20% reduction in I&I-related flows, saved almost 600 pumping hours and informed £2.4m investment
Building confidence: from pilot to business as usual
Beyond the immediate performance gains, the project delivered a shift in how Anglian Water approaches I&I management. Luke Murphy, Investigation & Resolution Manager at Anglian Water, highlighted the value of the data-driven methodology: “After rigorous testing of both the theory and the tool, it became clear that Stormharvester’s I&I tool significantly enhanced the precision of our investigations. The accuracy proved exceptional, saving considerable time and delivering tangible benefits. This data-driven methodology enabled us to adopt a Business-as-Usual approach, investigating infiltration and inflow at the most critical times of the year when it was likely to peak.”
This confidence is a critical outcome. Rather than treating I&I investigations as exceptional or reactive exercises, Anglian Water can now integrate analytics-led monitoring into routine operations. Seasonal peaks can be anticipated, resources deployed more efficiently, and interventions evaluated based on measurable outcomes.
A blueprint for smarter wastewater management
The project shifted I&I management into business as usual, enabling confident, evidence-based decisions at critical seasonal peaks
The collaboration between Anglian Water and Stormharvester demonstrates how advanced analytics can transform the management of complex wastewater challenges. By combining network data with sophisticated interpretation, the partnership delivered validation of existing operational knowledge, cost-effective and targeted interventions, improved environmental compliance, reduced public and environmental impact, and optimised investment planning for future AMP periods.
Most importantly, it showed that tackling inflow and infiltration does not have to rely on assumptions, intermittent surveys, or reactive responses. With the right data and tools, utilities can gain continuous insight into network behaviour and make confident, evidence-based decisions.
As climate pressures intensify and regulatory expectations continue to rise, the ability to extract value from existing data assets will become increasingly important. The Anglian Water case study offers a compelling example of how digital solutions like Stormharvester’s can unlock that value, turning hidden water into visible insight and insight into measurable impact. For utilities under increasing pressure to reduce pollution risk and optimise investment, this work demonstrates how analytics can turn I&I from a persistent uncertainty into a manageable, measurable operational variable.