Unacceptable quality blamed for Southern Water outages

Southern Water has revealed that unacceptable water quality levels were to blame for outages which left 25,000 households without water earlier this year.

The water company’s internal investigation report concludes that Hardham Water Supply Works in West Sussex was shut down in May due to a change in chlorine levels.

The report said that “this shutdown was triggered automatically when water quality levels fell below acceptable standards for water supply”.

It adds: “Our investigation has found that the probable cause was an unusual peak in turbidity (cloudiness) in the raw water entering the treatment works from the river and storage reservoir, leading to treatment challenges – in particular, chlorine dosing issues.

“This affected the clarification, filtration and disinfection treatment processes on site. This was made worse by a blockage of the main chlorine dosing system, because of calcification build up in the water softening system.”

The report adds that the cause of the contamination is unknown “as the catchment area that supplies the site has many potential sources that could have caused the issue, such as run off from crop growing farms (pesticides and fertiliser use), or dairy farms in the catchment or from industrial sources along the river”.

The automatic shutdown was triggered at 11.30pm on Friday 12 May cutting off supply to 25,000 homes. By the following Monday (15 May) supply had been restored to 22,500 customers, with supply restored to the remaining affected properties the following day.

Tim McMahon, Southern Water’s water director, said: “We are very sorry to those who were impacted by this disruption. We have carried out a thorough internal review into what happened, as it is vitally important we are transparent with customers when we fall short of expectations.

“Our investigations found that the water entering Hardham from the nearby river and storage reservoir was unusual in that it contained more sediment and impurities than normal, which caused difficulties for our treatment processes.

“Unfortunately, there is no way of knowing the exact source given the number of potential factors, such as agricultural and industrial run-off, but we have fully reviewed our own on-site policies and procedures so we are as prepared as we can be if this were to happen again.”

Southern has proposed a £63 million spend on improving the resilience of Hardham Water Supply Works between 2025 and 2033. It claims that the improvement would reduce risk of similar outages at the site by 80%.

Southern’s investigation report adds that 12,515 deliveries of bottled water were made to customers on the priority services register and local schools during the outages.

The firm was previously criticised by Ofwat for its response to water outages during freeze thaw events last year.