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Market update – Castle Water is the only water retailer fully tackling incorrect wholesale charges

Data available on the MOSL website demonstrates that Castle Water is the only retailer taking all possible steps to resolve customer problems resulting from wholesaler data errors, and no other retailer is doing so.

If you analyse the current Trading Disputes listed by the market operator, MOSL, 13 out of 17 have been raised by Castle Water. The remaining 4 are by retailers aimed at improving their own commercial position, for example, relating to trying to improve their payment terms to wholesalers.

Maintaining accurate data

The design of the non-household water market is based on the premise that each water company maintains accurate data, and corrects this data immediately when an error is identified. Data items used in calculating charges are set by wholesalers who own the water networks, and not retailers. In practise, this data is not always properly maintained by the wholesalers. There are legacy issues remaining from before the creation of the market in 2017. In addition, poor quality-control results in new errors occurring, for example when a meter is replaced. Water retailers are able to submit formal requests, known as bilaterals, to require data to be corrected. Data errors can have a material effect on bills – inaccurate data relating to a water meter can result in bills being significantly incorrect.

Castle Water has submitted 11,268 of these bilateral requests over the past 90 days. Of these, 75% are still outstanding, requiring further work by wholesalers. In some cases, these will be resolved by the wholesaler after a short period, in others, we are able to follow the dispute resolution process set out in the Market Codes: raising a “Trading Dispute”. Trading Disputes are necessary where we find major wholesaler failures which are not properly corrected – first, a data or pricing error, second a failure to complete the action required under the Codes.

Resource and expertise

Castle Water has the resource and expertise to mount this type of challenge – it looks as though other retailers either have no interest in doing so or are unable to commit the extensive resource required. There are currently 17 Trading Disputes listed on the MOSL website. Of these, 13 have been raised by Castle Water. The remaining 4 have been raised by independent and self-supply retailers. The 4 other Disputes all relate to the commercial terms between the retailers and wholesalers, and none relate to customers’ charges. It takes significant expertise and resource to raise and go through the required process for a Trading Dispute. It appears that only Castle Water is prepared to do this on behalf of its customers.

There is a further step that is available to water retailers beyond a Trading Dispute: Arbitration. As far as we are aware, only Castle Water has taken a dispute through to arbitration, and the output is expected shortly. This is important, as an Arbitration decision can provide important precedent and clarification to ensure charges are calculated properly, ensuring consistent interpretation of the Market Codes.

Mary Reynolds, Head of Industrial & Commercial at Castle Water said “The impact of challenges to wholesaler data can be material – and certainly can be significantly greater than the discounts offered by water retailers as an inducement to switch. Customers need to look at whether their water retailer is able to supply the resource and expertise to ensure wholesale charges are correct.”

Ray Porter, Director of Wholesale and Markets at Castle Water added “Castle Water commits very significant resources to ensure that water charges are correct. We see no evidence that other water retailers have the same expertise or resource”.

If you think you are being overcharged for your business water, or you’d like to learn more about how Castle Water can ensure your business pays a fair price for its water, contact Conor Kearney, Head of Business Development by email at