27 January

Drainage and Wastewater Management Plan Research


Wessex Water commissioned Accent and PJM Economics to undertake a research initiative aimed at exploring customer and stakeholder views in relation to the company's Drainage and Wastewater Management Plan (DWMP). This research initiative formed part of a broader customer engagement strategy which was to underpin the development of Wessex Water’s Business Plan for PR24. The research was focused on understanding customer views regarding sewer flooding, service improvements, billing timing and potential DWMP general options (GO).


The research process began with an immersive review of the results to date from previous research.

An expert co-creation panel was then assembled to discuss the DWMP, provide feedback on GOs and devise optimal customer communication strategies for these options.

Following this, a qualitative phase aimed to capture customer perceptions on wastewater drainage reactions to GOs, involving retailers, businesses, households, vulnerable individuals, and those who had encountered sewer flooding and wastewater issues.

The next stage involved two online stated preference surveys and supplementary face-to-face interviews among Wessex Water customers to ensure inclusivity among digitally disengaged customers. In total, 2,181 interviews were conducted, encompassing households, non-households, and vulnerable customers.

Survey A: 

- A pairwise choice experiment gauged the relative impact of different types of sewer flooding on customers.

- A contingent valuation exercise to measure customers’ willingness to pay for a package of sewer flooding service level improvements

- A choice experiment to measure customers’ preferred timing of investment in sewer flooding service level improvements

Survey B:

- A pairwise measure to measure customers’ preferences and willingness to pay with respect to different impacts of the GOs.

- An exercise focused on measuring customer support for the various GOs.

The data were weighted to be representative of the profile of Wessex Water customer base.


Results were obtained on customers preference weights with respect to different types of sewer flooding; their wllingness to pay for reduced flooding, and their preferred timing of investment.  

Comparisons of the acceptability of GOs were drawn, revealing which emerged as most, and least, acceptable and appealing to customers. 

Customer segmentations were examined including region, age, gender, and segmentation code.

On the basis of supporting validity evidence, the results obtained were recommended as robust and reliable for use in Wessex Water’s DWMP.