The source of the outbreak was located at Pitsford Reservoir
Householders have been told their tap water is safe to drink again, after supplies to thousand of homes became infected with a sickness bug.
At the height of the scare, 250,000 Anglian Water customers in Northamptonshire were affected.
Anglian said it had lifted its restrictions following work to treat the cryptosporidium parasite which had got into the system.
Customers will receive goodwill payments totalling nearly �3m.
The microscopic bug can cause severe stomach upsets, especially in young or elderly people.
An Anglian Water spokesman said the decision to lift the notice had been made with the Health Authority and Local Authorities.
He said: "The decision to lift the notice for all affected customers has been taken following an accelerated cleaning and flushing programme over the week.
The scare affected an area containing 250,000 people
"Anglian Water would like to thank its employees and suppliers who have worked tirelessly to make this possible."
The spokesman said green all-clear notices would be posted to Northampton customers on Friday night and notices for people in Daventry would be sent over the weekend.
He added: "Anglian Water is to make a goodwill payment to customers in Northampton, Daventry and the surrounding areas for the inconvenience caused by the boil notice put in place on Wednesday 25 June after tests detected cryptosporidium in the water supply.
"It is estimated that total goodwill payments will approach �3m and this cost will not be passed on to customers in any form.
"The payment will be made in the form of a credit equivalent to six weeks' free water supply, based on customers' past annual water bills.
"This will be up to a maximum of �30 per household and full details will follow in a letter to customers."
'Delighted by news'
Cases where businesses think they deserve a further goodwill payment will be considered individually.
Anglian Water Chief Executive Jonson Cox said: "Our customers have been understanding, patient and helpful throughout this incident.
"I am delighted that today we are able to lift this notice for all of those affected."
Last week's announcement led to schools being closed, supermarkets running out of bottled water, and warnings that the crisis could last for weeks.
The company traced the contamination to the Pitsford Water Treatment Works and treated it with ultraviolet light
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