Anglian Water said that, before the cryptosporidium bug was detected in Pitsford Reservoir, it had 300 WaterCare customers – a number which has rocketed to 1400.

Sara Rowland, a spokeswoman for the water company, said: "It's a lot more people but that's actually brilliant that they are contacting us.

"Some people have a visual or hearing impairment which means they hdn't heard about the scheme previously.

"Before this we obviously didn't know about them and if we don't know you are out there, we can't help you."

Anglian Water delivered 69,000 bottles of water –about 100,00 litres - over the weekend to WaterCare customers which included hospitals, nursing homes and some schools, to prepare them for the week ahead.

The notices to boil water should be lifted by the end of the week for about 50,000 homes and businesses nearest Pitsford Reservoir.

The ultra-violet treatment aimed at killing the bug was still incomplete on Sunday evening despite the efforts of 230 microbiologists and other scientists.

Once the water is treated, the system needs to be flushed out then re-tested, a process which the water company warned may see fluctuations in tap water pressure.

Despite the inconveniences, Anglian Water said it has not yet had discussions about possible cash compensation to customers.

Mrs Rowland said: "It has been all hands on deck literally 24 hours a day since the late hours Tuesday.

"Without having a real idea of how long it will go on for how can you start to address compensation?

"But it is definitely something we will be looking into.

She added: "We do apologise but all this work we are doing is with community health and safety in mind."