The water supply to thousands of homes in the north has been branded so bad that even cattle and dogs do not want to drink it.
Customers in the Spey Valley have fought a four-year battle over the foul-tasting “swamp water”.
But they have been left dismayed at Scottish Water’s plans to improve it – by adding a cocktail of ammonia and chlorine.
The move will affect more than 10,000 homes between Grantown and Newtonmore.
Farmer John Kirk, of Rothiemoon at Nethy Bridge, said his property used to receive “crystal clear” supplies from Loch Einich in the Cairngorms.
But he claimed that changed after Scottish Water opened a £24million treatment works at Aviemore in 2012 and started taking supplies from an underground aquifer via boreholes.
Mr Kirk said: “It took the cows a long time before they would drink it because of the horrible, stagnant smell.
“They drink it now because they don’t have a choice, but they don’t like it and my four working collies are the same.
“If you give an animal a choice of Aviemore tap water or spring water, they will choose the spring water every time.”
He added that he had bought a charcoal kettle because his tea tasted so bad.
Highland councillor Bill Lobban, of Aviemore, said: “The aquifer supply is like foul-tasting swamp water.
“We don’t know how long it has been there and it tastes and smells absolutely disgusting.
“Hundreds of people have complained, but Scottish Water maintained there was nothing wrong with it and it was perfectly safe to drink.
“That may be true, but it still tastes awful and has a very heavy chemical smell.”
Scottish Water now plans to “chloraminate” the supply, a process, which involves adding chlorine and very small quantities of ammonia.
But residents are worried about the move and have called for independent scientific evidence to support it.
Councillor Lobban, who has installed a whole-house water filter, said chloramination would involve adding further chemicals to the supply.
He said: “I’m not a scientist.
“I don’t know whether it’s bad or good so I want some independent scientific evidence that what they are going to do is the best thing and not just the cheap option.”
Scottish Water claimed the treatment works had improved the quality of the tap water in the area, ensuring it met all strict regulatory standards.
However, it admitted that a “small number of customers” had found chlorine levels – necessary to ensure the water quality was safe – not to their taste.
The company’s strategic customer service planning director, Simon Parsons, said: “We have been listening carefully to our customers and working with our operational teams to find the right solution to ensure that everyone enjoys this new supply.
“We remain committed to continuing to listen and work with the community.”
