DWI notes compliance improvements but says more work is needed

The Drinking Water Inspectorate has reported steady improvements to water quality compliance tests over the past two years but noted more work is needed.

The Compliance Risk Index (CRI), which assesses treatment works, supply points, service reservoirs and consumer taps, was 2.80 for England and 2.87 for England and Wales for 2019 with a lower value indicating lower risk. This improved from 3.87 in 2018 with notable change attributable to supply points.

Southern, Yorkshire, South West, Northumbrian, Severn Trent, Cambridge, South Staffs, United Utilities and South East Water each had CRI scores above the 2.80 level.

The annual Drinking Water 2019 report found that compliance failures were dominated by coliforms (type of bacteria) and turbidity (water discolouration due to particles being present) at treatment works, where asset condition posed a significant risk to water quality.

The DWI said another “recurring theme” in compliance failures was “water companies’ inability to address the structural risks promptly” at treatment works. It advised companies to review their works and take steps to address the risks of accessing tanks.

The report noted overall improvements from Southern, Affinity, South Staffs and Severn Trent. However, of those four only Affinity improved sufficiently to be within the industry CRI. Southern’s CRI remained four times above the average for England despite falling by 13.18 from the previous year.

The DWI also noted a “noticeable deterioration” in the scores from Yorkshire, Bristol, Cambridge, South West, Northumbrian and United Utilities.

The indicator is designed to allocate a numerical value to risk, the lower the number the lower the risk. For 2019 the CRI was 2.80 for England and the industry median value was 1.73 with half the companies meeting the expectation.

From 2020 onwards Ofwat has set a target CRI of 2 for all companies, which has been set upon a median value that DWI describes as being reasonably stable for the past three years. DWI said that with more than half of companies meeting the outcome “it is not unreasonable for all companies to achieve this given that in some instances failure to meet this CRI has been entirely within their control.”

Increased heavy rainfall and growing demand for water supplies were noted as adding pressure to water quality.

During 2019 the water companies collectively carried out 3,502,637 sample tests, of which 1,509 failed to meet one or more of the standards set down in the regulations or exceeded a screening value.

The report said 94 per cent of hazards identified by companies’ risk assessments are being effectively mitigated and the remaining six per cent are related to domestic plumbing. The DWI said this “illustrates the high standards companies hold themselves to in securing good clean drinking water”.

Despite the compliance failures the report said: “The status of water quality in England is at a very high standard but work remains to improve planning for future generations.”

This work included 577 recommendations to individual companies to address specific issues at treatment works, supply points and service reservoirs as appropriate.

The report went on to note ongoing concerns that taps containing nickel and piping made with lead on customer properties are exposing consumers to risks from water supplies.

The inspectorate said lead piping in domestic plumbing systems will continue to pose a risk to the mental and physical health of the population until it is removed.