Severn Trent Water

26 May 2022


Severn Trent Water


Severn Trent Water (STW) is one of the largest water and waste companies operating within England and Wales. As part of their OFWAT commitment to significantly reduce burst and leakage within the current 5 year AMP cycle, they were seeking partners to optimise the pressure management and control within a challenging district metered area (DMA) with a service reservoir in order to reduce leakage, reduce the expected bursts and to calm the network through control optimisation.

This was to be achieved through a combination of advanced monitoring and actuation (Pressure/flow/time) coupled with detailed hydraulic analysis.

Inflowmatix were awarded the contract to use their InflowSense™ ‘Edge’ high frequency devices for the necessary spatial coverage in conjunction with Cla-Val and their D12 Pressure Management Controller.

The 5 month study focused on the Hoo-Ash network area with a total pipeline length of 20 km and included a mix of domestic and industrial consumers.


Following a review of the network area Inflowmatix deployed 5 InflowSense™ ‘Edge’ devices (with GPS measured elevation), with Cla-Val installing their D12 Controller onto the existing aged 100mm 90GE-01 PRV, linked to the Cla-Val Link2Valve™ platform.

Installing multiple InflowSense™ ‘Edge’ devices enabled the geo-spatial coverage of the area to elicit the required high frequency data points in conjunction with elevation/pressure/flow from the D12 controller at the DMA inlet. This enabled iterative optimisation of the average zonal pressure (AZP) while capturing and maintaining the pressure at the critical point. Applying device spatial coverage in this manner enables a comprehensive solution as opposed to measuring/optimising at a single critical point, which simply transfers the problem elsewhere within the network.

The Inflowmatix pressure management solution was used to perform a hydraulic analysis of the area based on the incoming pressure/flow/elevation measurements, resulting in a pressure/flow valve control curve that optimises the average zonal pressure (AZP) whilst maintaining the critical point (CP) adhering to minimum pressures throughout the network in order to ensure customer supply.

Implementing this control curve and monitoring the results allowed for a second iteration of the optimisation process to overcome the Hoo Ash Service Reservoir (SR) filling regime which took place at infrequent times over a 24 hours period. Further analysis of the network hydraulics led to a joint decision to switch the valve control to time v pressure basis during night hours, whilst reverting to dynamic pressure v flow control for the rest of the day.


The implementation of the optimised pressure v flow control curve resulted in a significant reduction of pressure across the network during high-pressure periods such as the night time, while providing confidence that low pressure levels at critical sites did not fall below customer requirements. The second iteration of the optimisation process (time v pressure through the remote flexibility of the Cla-Val D12 controller/Link2Valves™ platform) resulted in a further reduction of night pressure without impacting processes such as the filling of the service reservoir.

Using STW’s own data points, this resulted in a 33% leakage reduction (31m3/day) and 12% actual burst reduction.


De Watergroep is the biggest drinking water and industrial water company in the Flanders, the northern region of Belgium. They were aware of large pressure transients occurring in parts of their distribution network. As such, they were looking for a partner to investigate the issue using advanced monitoring and hydraulic analysis techniques. Depending on the outcomes of these tests, they intended to implement corrective actions at localised event sources to achieve greater consistency in the pressure across the water network.

Following a competitive process, Inflowmatix was awarded the contract. Our InflowSense™ ‘Edge’ high-frequency devices were subsequently deployed to help De Watergroep identify the time, magnitude and frequency of transient events within their network. They assisted in identifying the source location of events, allowing targeted remedial actions.

The five-month study focused on 8 District Metered Areas (DMA’s) in the municipality of Heuvelland and Poperinge. The pipeline had a total length of 624 kilometres (388 miles). It served a mix of domestic and industrial consumers

Our collaboration with Inflowmatix was very beneficial. Their ‘localisation’ algorithm and Cumulative Induced Pressure Stress metric (CPIS™) delivered excellent insights that would not have been identifiable otherwise.

Francis Volckaert – Program Manager Asset Information, De Watergroep


Based on a collaborative review of the area, Inflowmatix partner SUEZ/CNS, deployed 45 InflowSense™ ‘Edge’ devices. This covered a number of strategic locations typically associated with pressure-transient behaviour.

The pressure profiles in the area being examined were characterised using our Cumulative Pressure Induced Stress metric (CPIS™). It provided an understanding of the overall network performance. The metric also revealed the impact from changes in network control and consumer behaviour.

The high-frequency (128 S/s) event-detection algorithm captured and characterised the magnitude and frequency of potentially damaging pressure-transient behaviour within all the district metered areas. Source localisation was performed to further analyse the cause of these pressure-transient events. Targeted remedial action plans were implemented.


In the municipality of Heuvelland, the InflowSense™ ‘Edge’ devices detected a regularly recurring event: a pressure drop of 20-30 mH2O over short periods of time. This gave rise to severe pressure transients that propagated through the network with a magnitude of up to 130 mH2O.

The highest pressure transient impact was captured at, and initially attributed to, a local tree nursery. However, results from event localisation pointed to an area within 20 metres of a different industrial user, which was identified as the source.

Our Cumulative Pressure Induced Stress metric and hydraulic ‘event’ analysis delivered insights that uncovered the magnitude, frequency and overall impact of the ‘event’, and accurately located the source. Armed with clear and measured information, De Watergroep was then able to implement a targeted remedial action plan to reduce transient impact and achieve greater consistency in the water network.


NRW losses and bursts are a major cost to water companies. Portsmouth Water is keen to prolong the life of the mains by locating leakage at source by identifying where it will happen, root causes and reducing the number of leaks. The strategy now focuses on prolonging the life of critical assets by introducing calming measures and implementing strategies to mitigate leakage at source.

Portsmouth Water were keen to focus on proactive monitoring and detecting issues before they worsened or became critical operationally. Magnified by the unprecedented demand over the previous months and driven by Covid-19, demand stayed at weekend levels with no reduction during weekdays. Higher demand caused excessive strain on the network and on pressure management in particular.


Inflowmatix and Portsmouth Water identified a unique opportunity to mitigate potential failures in their Pressure Managed Zones by extensively deploying InflowSense™ Edge high frequency pressure monitoring devices coupled with its
new ‘service’ based product offering arboricity™. Approximately 50 InflowSense™ Edge devices were deployed alongside existing sensors in order to provide temporal and spatial coverage of the zones, to comprehensively characterise the

arboricity™ has a state-of-the-art hydraulics analytical engine built in, and uses this engine to ensure outcomes are always meaningful and drive behavioural change.

Understanding the network and its hydraulic behaviour is often embedded knowledge within the workforce, but access to wider groups in the company is limited. arboricity™ generates this understanding through the near real-time calibration and continuous refinement of hydraulic models. Recognising personnel have different oversight of their assets and network, individual, targeted registration enables stakeholders to receive relevant actionable outcomes.

The arboricity platform is giving us the ability to understand how our network is performing in a lot more detail

Jim Barker

Head of Water Resources, Portsmouth Water Ltd


arboricity™ quickly demonstrated insightful results building a model which learns network behaviour and identifies anomalous activity. This was evidenced through analysis of the Westergate area where early intervention would have avoided a significant PRV malfunction which led to multiple bursts and impacted a significant number of properties several hours later.

Another area, Staunton Street showed a high CPIS™ measurement, investigation identified pumps from apartment blocks were causing the anomalous activity, calming measures were introduced dramatically reducing CPIS™ scores to a more acceptable level and mitigating potential failure of the network.

Inflowmatix is now working with Portsmouth to implement hybrid hydraulic and statistical tools across the region to further mitigate costly and disruptive events.


Yorkshire Water (YW) manages 31,000km of clean water network in the UK providing 1.24 billion litres of potable water each day.

A principal regulatory challenge is the reduction of leakage within the network. Inflowmatix was approached to help with this challenge – in areas prone to bursts and leaks.  

One of these district metered areas (DMA’s) was Fox Street. Fox Street is a pressure man aged area of Sheffield controlled through a PRV. The area is largely residential, with some light industrial users.  

As this area had a moderate burst and leak rate, YW deployed a number of high frequency (HF) InflowSense™ ‘Edge’ devices to get a better understanding of the underlying issues within the DMA. 


Over a number of days our Cumulative Pressure Induced Stress (CPIS™) metric showed a significant increase in dynamic activity indicating a prelude to a burst.   

In parallel with this, the existing YW alerting system of night line usage indicated there was a probable burst due to increase in demand. The burst was fixed and back ground pressure returned to normal. However an unsteady state was still indicated by the underlying CPIS™ metric.  

Collaboratively a further step of source localisation was undertaken which highlighted secondary issues with the PRV. Further investigation observed the PRV to be hammering and hunting for optimal pressure.  

Adjustments to the PRV were completed and checked against a standard 1-min interval pressure logger.  


Post field adjustments, further inspection using 128s/s summary data, raw data downloads and CPIS™ metric confirmed the PRV behaviour remained unstable with a 5 metre pressure variation over 0.2 second period being observed. This concluded the PRV was oversized and needed replacement.

Without the detailed insight from the Inflowmatix high frequency InflowSense™ ‘Edge’ devices, CPIS™ and InflowSys™ platform the root cause of the problem would have been undiscovered and the instability  within the network would have remained.


On the morning of Saturday 27th May 2017, an 8” cast Iron trunk main carrying water from a reservoir to the area of Sea Mills burst. The network isolation to repair the pipe resulted in loss of water supply to around 4,000 properties between 12 and 30 hours, over the bank holiday weekend.  

Costs associated with the repair were estimated to be in the region of £8,000 plus additional costs for water supply provision, regulatory penalties and negative publicity. Bristol Water needed to understand the contributory factors ( hydraulics, pressure related transients) in order to get to the root cause of the failure quickly and apply any lessons learnt to similar high risk scenarios. The network topology contained a pumping station, reservoir outlet valve and non return valve feeding two District Metered Areas (DMAs). 

Bristol Water chose to work with Inflowmatix to establish where pressure related risks existed within their network and how these may have contributed to the pipe failure.


Inflowmatix consulted with Bristol Water to establish the optimum location of 24 InflowSense™ high frequency pressure monitoring deployments. These captured high resolution pressure data at 128 samples/second, significantly higher than a standard pressure logger or telemetry data (15 minute average) with analytics performed on the InflowSys™ platform. The results were displayed directly to the Bristol Water leakage team through the InflowNet™ application. A valuable metric captured and plotted was the Cumulative Pressure Induced Stress (CPIS™) index – a pipe stress index developed by Imperial College London correlating transients effects with pipe stress through fracture mechanics.

Working with Inflowmatix has significantly helped Bristol Water to understand the hydraulic behaviour of part of our Network previously affected by a major mains failure.

Frank van der Kleij

Head of Asset Risk & Planning, Bristol Water Plc


Using a high density of smart InflowSense™ devices combined with the InflowSys™ analytics platform, Inflowmatix were able to provide Bristol Water with a clear understanding of the hydraulic conditions and operation of their network and conclude useful refinements of their geospatial map/modelling for future benefit.

From the data insights captured, Inflowmatix were able to provide Bristol Water with a valuable view relating to the network topology within the ‘burst’ region.


Severn Trent were suffering a series of high pressure burst incidents within a densely populated area, significantly impacting a large volume of customers and attracting negative publicity both locally and nationally. It was important to identify the underlying cause of the problem quickly. In order to do this Severn Trent selected an innovative approach using high frequency transient monitoring detection analytics.


Inflowmatix recognises that traditional 15 minute average data monitoring of a water network is unable to capture the detail of strategic asset performance and the impact on the network infrastructure during large multi event (i.e.pump/booster station/ valve operation) variations in water flow of a network. By deploying the leading data analytics suite – InflowSys™, high resolution pressure data was captured and analysed in real time to identify transient sources and dynamic pressure variability causing network asset fatigue and hence burst failure. The asset fatigue was measured using the InflowSys™ Cumulative Pressure Induced Stress index (CPIS™) in order to prioritise future potential at risk areas.


The outcomes far exceeded the business case:

• 70% reduction in burst rate

• £60k/€70k OPEX repair savings per annum

• 3 month payback on £12k/€14k improvement costs

Severn Trent Water identified greater efficiency by evaluating the operational investigations that were conducted and monitoring how these were resolved to improve the network performance.


Wessex Water were looking for innovative approaches  for burst/leakage reduction and network control in order to accelerate their upper quartile ODI performance and provide a truly enhanced customer experience. 

To reduce average zonal pressure (AZP) whilst maintaining the networks critical points (CP’s) in an automated manner required the building of a ‘reduced’ hydraulic  network model through accurately computed algorithms using principle variables (flow,  pressure, elevation, HF spacial coverage/sampling) in conjunction with the PRV/ Controller manufacture Cla-Val.  


Post due diligence and planning a number of  InflowSense™ HF pressure monitoring devices were deployed (with GPS measured elevation) linked to the InflowSolve™ data analytics platform and Cla-Val Link2Valves™ platform via the Cla-Val D12 controller (pressure/flow).  

The InflowSense™ devices captured the high-resolution pressure data at 128 samples/ second, significantly higher than standard pressure logger or telemetry data (15 minute average). The in-sights of dynamic pressure  variability and transient sources were displayed to Wessex via the InflowSys™ application immediately post deployment.  

The key data points (pressure/flow/HF data, elevation) were securely captured from the InflowSense™ HF devices and Cla-Val D12 controller from which a ‘reduced’ hydraulic model was dynamically computed to obtain an optimal flow/control curve. This was then automatically issued to the Cla-Val Link2Valves™ platform for client acceptance. From this an optimal  ‘flight-path’ of reduced AZP was created to optimise DG2/3 and maintain the supply of users. 


Using a combination of the total InflowSys™ analytics platform and the Cla-Val Link2Valves™ platforms has provided a clear understanding of the dynamic hydraulic conditions and operation of the network.  The successful outcomes have provided Wessex Water with a clear ‘glide-path’ down to a >30% reduction in AZP/leakage whilst maintaining customer supply.  


United Utilities were looking to trial a novel dynamic pressure management solution to assist with network calming within a particularly challenging DMA. The DMA was a mixture of domestic and commercial properties with large elevation variance and pressure fluctuations thought to be the result of fast demand changes caused by industrial users and a pumping station located to the north of the DMA.

The objective was to ‘calm’ the DMA whilst maintaining the network’s critical point (CP) in an automated manner to extend asset life and eradicate burst events. This required the building of an equivalent network (EN International Patent Application No: PCT/GB2019/052992) model, accurately computed algorithms using principal variables (flow, pressure, elevation, high frequency (HF) spatial coverage/sampling) in conjunction with the Cla-Val PRV and self powered PRV D12 Controller. 


Upon the completion of due diligence and planning, a number of InflowSense™ High Frequency (HF) pressure monitoring devices were deployed (with GPS measured elevations) linked to the InflowSolve™ data analytics platform. Additionally, the existing PRV was replaced with a Cla-Val 100mm GE-D12-99- 01 Pressure Management valve linked to the Cla-Val Link2Valves™ web platform via the Cla-Val D12 intelligent valve controller. The valve was initially set to a fixed outlet pressure in order to gather baseline data (pre-modulation).

The key data points (pressure/flow/HF data, elevation) from the InflowSense™ HF devices and Cla-Val D12 controller created an EN model enabling the production of a series of PRV flow/control curves. The close proximity of the PRV to the CP required a further creative approach of translating the CP target to the nearest monitored asset. By doing this, an optimal ‘flight-path’ of PRV flow/control curves using a ‘relative hydraulic relationship’ were successively issued to the Cla-Val D12 controller for actuation which achieved network calming.

Working collaboratively with Inflowmatix and Cla-Val gave considerable insight into a challenging area of our distribution network. This enabled us to improve performance beyond what could be achieved with typical network calming approaches. This is already delivering service benefits for customers and – by extending asset life – will continue to do so for the future

Matthew Holmes

United Utilities Network Performance Engineer


Using a combination of InflowSys™ analytics, the Cla-Val Link2Valves™ platform and an optimally sized PRV, enabled: