Thousands of people in north Wales can stop boiling their drinking water two months after the area was affected by an outbreak of stomach illness.
The reservoir is the "probable source" of the outbreak
Health officials announced on Monday that the cryptosporidium outbreak in Anglesey and Gwynedd was over.
A total of 231 people whose water came from the Cwellyn reservoir in Snowdonia caught the bug, it was confirmed.
Welsh Water customers affected by the outbreak will receive a £25 cheque towards the inconvenience.
Dwr Cymru Welsh Water said it was pleased customers were no longer being inconvenienced.
Managing director Nigel Annett said: "In the exceptional circumstances of this outbreak we decided to install the new equipment as an added precautionary measure. We are now sure that it is safe to lift the boil water notice."
But he said Welsh Water had not "done anything wrong".
He said: "The water treatment works and our water supply system has been operating perfectly normally throughout the whole period.
"But we did recognise that asking people - under advice from the health experts - to boil their water for drinking purposes over Christmas and new year was a massive inconvenience and a massive cost."
The company said the £25 payment offered to customers was not an indication of any breach in quality standards, but was the average price of water for two months.
Seventy thousand people were originally told to boil their drinking water or take bottled supplies when the first cases emerged in November.
The order was due to have been lifted earlier this month but that was delayed while improvements were made to the water treatment works at Cwellyn.
The outbreak control team said all the 231 cases have been directly linked to this outbreak.
There have been no new cases of the bug detected in the last two weeks.
In a statement, the control team also said: "All the available evidence and expert opinion point to Llyn Cwellyn being the probable source of the outbreak. There is no alternative explanation."
Mark Bartlett, who runs the Gwynedd hotel in Llanberis, said the last few months had been "extremely difficult".
He told BBC Radio Wales: "It's small things that people don't even think about. For instance Coca-cola and lemonade on tap: you can't use those because they're coming straight out of the mains water.
"Even cleaning out your beer pipes. Imagine how much water you have to pre-boil to clear nine or 10 lines of beer. We get through gallons and gallons of water."
He said sales of spirits and shorts had dropped by 90% because people could not have ice in their drinks and estimated he had lost "several thousand" pounds during the outbreak.
Mr Annett said they would talk to customers like Mr Bartlett to see what the company could do to help.
He added: "By and large this was a public health problem which might or might or might not have implicated the water supply and we had to do the right thing to protect to public health."