WANDa PLDR: Water pipe-level discoloration assessment tool

Project summary

Discoloration events are one of the most common causes of drinking water complaints, yet the flushing programmes used to manage them have traditionally been manual, inconsistent and slow to scale. To address this, WRc developed the WANDa PLDR (standing for ‘pipe-level discoloration risk’), which automates flushing design by combining hydraulic, geographic information system (GIS) and customer-contact data into a single pipe-level risk score. It is now live across three major UK water companies – Severn Trent Water, United Utilities and Southern Water – and is fast becoming the industry’s benchmark approach to discoloration risk management.

The background

WRc identified the opportunity to automate and standardise flushing design by combining hydraulic, GIS and customer contact data. Building on the existing WANDa platform – a water network support tool driven by hydraulic modelling and GIS data – the team created a bespoke analytical application that transforms these datasets into clear, optimised flushing plans.

WANDa PLDR assesses pipe-level discoloration risk, selects the most effective hydrants and calculates efficient flushing sequences. Its innovative methodology combines diurnal velocity profiling with iterative hydrant-effectiveness analysis, enabling targeted, operationally efficient programmes in place of blanket, calendar-based flushing.

With active deployment across Severn Trent Water, United Utilities and Southern Water, WANDa PLDR is an operational, multi-client product that is reshaping how discoloration risk is managed across the UK water industry and is well positioned to become the industry standard.

Severn Trent Water is WRc’s longest-standing partner in this work and in 2026, is in its third year of a rolling framework software as a service (SaaS) agreement covering network analysis and PLDR, building on several years of earlier project work that shaped the application into its current form. United Utilities and Southern Water have been partners since early 2025 to co-develop purpose-built PLDR applications; both are now finalising the scope for a second 12-month term, extending the SaaS agreement and adding further application functionality alongside continued project work.

Multidisciplinary strategy

The solution has been developed and deployed in active, ongoing partnership with three major UK water utilities, each contributing a different dimension to its evolution.

Severn Trent Water was the first UK water company to deploy regional maintenance flushing at scale and is the pioneer behind this approach. Years of continuous project work have directly shaped the discoloration risk methodology tool. That sustained, trusted relationship has opened the door to larger, more in-depth studies and projects with Severn Trent Water across the wider WANDa platform.

United Utilities engaged with the project from inception through to full network deployment, contributing operational, water quality, asset strategy and modelling expertise throughout. United Utilities has scaled its PLDR flushing from zero to an industry-leading level, often completing flushing across more than 200 district metered areas in a single month, reflecting the depth of operational commitment and confidence placed in the solution by United Utilities teams.

Southern Water has contributed operational and water-quality expertise as its own purpose-built application was finalised.

The challenges

• Scaling analysis across regional datasets: Managing and processing hundreds of hydraulic models alongside GIS and customer-contact data at regional scale, across multiple large water-company networks, was a significant technical challenge.
• Displacing an established, costly method: Discoloration risk had historically been managed through unidirectional flushing, a resource-intensive method requiring extensive plan generation and site works. Moving each client to a targeted, pipe-level risk-based alternative required new operational thinking and confidence in a fundamentally different way of working.
• Bespoke integration across three organisations: Although all three clients share the same goal – reducing discoloration contacts – each operates with different working practices, internal processes and stakeholder structures. Each application has had to be built bespoke to its client’s requirements and processes; the more seamlessly it fits within a client’s existing systems and workflows, the greater the efficiency and value it delivers.

The solutions

Developing the tool combined collaborative design, rigorous data integration and iterative digital development to tackle this long-standing industry challenge. Working in close partnership with client stakeholders across operations, water quality, asset strategy and hydraulic modelling teams meant that the objectives, data requirements and success measures needed to be defined collectively from the outset, ensuring the solution was shaped by real-world operational requirements at every stage. This collaboration with clients was integral to the process, with their expertise, data and co-investment all contributing directly to the development.

Following the initial inception phase, a detailed baseline review was undertaken covering hydraulic-model-to-GIS alignment, historical discoloration contact analysis and validation of hydrant and asset data. This established a reliable analytical foundation before any development work began.

The impact

United Utilities and Southern Water have both reported reductions in discoloration-related customer contacts since the service was deployed, reflecting direct improvements in drinking water quality, customer satisfaction and regulatory performance. Severn Trent Water’s longer track record with the underlying approach demonstrates the same benefits sustained over multiple years.

The solution has also reduced planning time, improved the efficiency of flushing operations through optimised sequencing and targeted interventions and proven substantially more cost-efficient than the historical method of unidirectional flushing, which requires extensive plan generation and site works. It has generated rich datasets that are already informing wider asset strategy decisions, including maintenance prioritisation, sampling and network renewal planning.

The developed solution aligns strongly with four UN Sustainable Development Goals:

• SDG 6 – Clean Water and Sanitation: improved water quality and reduced discoloration events for customers of three major UK water companies
• SDG 9 – Industry, Innovation and Infrastructure: scalable digital infrastructure deployed for essential public services
• SDG 12 – Responsible Consumption and Production: reduced water use and operational waste through optimised flushing volumes
• SDG 13 – Climate Action: lower operational carbon through more efficient programme delivery and fewer vehicle movements.

With three major UK water companies already realising the benefits, WANDa PLDR is fast becoming the reference approach to discoloration risk management in the UK water sector. The WRc digital team is working with more water companies to explore how a smarter, data-led alternative to traditional flushing could reduce their own contact numbers and operating costs.