The company said the risk to customers' health was believed to be low and they hoped to lift restrictions on Thursday or Friday.

People in Darlington were warned to boil their water as a temporary precaution following the fault at Broken Scar Treatment Works in Darlington in the early hours of Tuesday.

Now the water company has reacted to questions, criticisms and concerns aired at a Darlington Borough Council meeting on Tuesday night.

Read more: Northumbrian Water response to Darlington fault 'shambolic'

Councillor Kevin Nicholson, cabinet member for health and housing, said Northumbrian Water "knew about the incident a little bit longer that had been advertised".

He said he had expressed concerns that they "weren't moving quick enough" and was "disappointed with the slow pace at which Northumbrian Water operated and acted".

Cllr Stephen Harker said he was gravely concerned and told the meeting: "I do feel that it has been perhaps shambolic in terms of the speed with which they've chosen to act."

Cllr Kevin Nicholson

Keith Haslett, Water Director for Northumbrian Water said: “As soon as we were made aware that there had been a fault at our Broken Scar treatment works, we kicked into action to diagnose the fault and understand what had happened, and to assess the impact of risk for water quality.

“Protecting our customers’ health is our number one priority and once we had a clearer picture of the problem, we immediately notified our health colleagues at UKHSA (UK Health Security Agency) to understand the next steps and processes.

“We reached the joint decision that there was some level of risk to customers’ health, although we believed this risk to be low, and as such we needed to notify people of the precautionary warning.

“We worked hard to establish the facts and make sure that our messaging and advice was correct and up to date, and that we could mobilise resources and support for our customers as soon as the message was out there.

Read more: Readers react to Northumbrian Water's Darlington alert

“This has been a very large operation and we have had hundreds of volunteers hand-delivering more than 32,000 date-stamped notices across the affected area, text messages have been sent directly to around 24,000 customers, and we’ve spoken to many more on the phone.

“We’ve also delivered more than 20,000 bottles of water to 60 schools, 25 nurseries and over 300 priority service customers within the impacted area.

“We’re very sorry for any issues this has caused our customers, but we’d like to thank the people of Darlington for working with us, and the UKSHA for their support and guidance.

"As with everything we do, we’ll review this once it’s finished and will learn from this going forward and how we can improve.

“Our test results are coming back clear and if this continues, we’re hopeful of being able to lift the restrictions on Thursday or Friday.

"We will work hard to keep customers informed every step of the way.”

Broken Scar. Picture: Sarah Caldecott

A spokesman for Northumbrian Water said: "The fault at Broken Scar was identified in the early hours of Tuesday morning.

"Although the fix was done very quickly, we needed time to fully diagnose the problem, assess the impact this had on our network and understand whether it posed a risk to our customers. 

"It wasn’t until Tuesday mid-morning, after carrying out tests and enquiries, did we know what exactly the situation was.

"As soon as we knew this information, we shared it immediately with the UK Health Security Agency and the Drinking Water Inspectorate before we could take any further action."

The spokesman said they contacted health colleagues as soon as they had a clear picture of the impact, agreed the next steps with them and came to a joint decision around noon to put out a precautionary warning.

"The short time period after this was crucial to make sure that our communications were clear and factual, and that we could immediately mobilise resources to notify and support the 32,000 properties affected.

"Following the joint decision that a precautionary boil notice would be advised to customers, we worked with our colleagues at UKHSA to prepare clear and factual communications.

"This included making sure we had the correct, up to date information and advice available for our customers, as well as where they could go for support. The precautionary message was put out shortly after 3pm."

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