A Havelock North family cannot use the water in their home "without fear", as they believe the chlorine used in the suburb's water supply is reacting with their water piping.
The water supply was chlorinated as a safety measure following its contamination with E.Coli in early August, which left more than 5000 people sick with campylobactor.
When Havelock North resident Rachael Campbell ran a bath for the first time since the gastro outbreak, she was surprised to find the water coming from the taps was blue.
As well as the unusual colour, the water also had a musty and "vile" smell.
The Guthrie Rd resident said that while her 8-year-old daughter Roxane had been in the bath, she began complaining that it felt like "her skin was burning".
"It was stinging, my daughter couldn't stand being in it," Ms Campbell said. After being in contact with the water herself, she said her hands became red and inflamed.
A week since the event, Roxane was still "not overly fond of the idea" of hopping back in the bath, the water in their bathroom "smelt vile", and the plants which Ms Campbell had watered from the tap had died.
"At the end of the day you shouldn't have to be in fear of what's coming out of your tap, in this day and age, and in Hawke's Bay," she said. "We can't turn on the tap in my house without fear."
Ms Campbell had spoken to others in Havelock North who had noticed similar things, and now believed the issues with her water stemmed from a reaction between the suburb's chlorinated supply, and copper piping within her home.
Victoria University School of Chemical and Physical Sciences senior lecturer Robin Fulton said copper salts did form a blue colour in solution, and acidic water could cause copper pipes to corrode, also creating a blue colour.
"Whether the chlorination process is causing the potential corrosion will depend on what type of chlorination agent they are using," she said. "Chlorine will not directly react with the copper pipes unless heated to a very high temperature. But a byproduct of the chlorination agent could potentially cause problems."
Ms Campbell said she thought the council should be actively asking residents of their concerns.
A spokeswoman for Hastings District Council said they had no other similar reports made from residents.
Hastings mayor Lawrence Yule spoke to Ms Campbell personally, and said staff had conducted tests of her water, which indicated there was no e.Coli present.
They had also conducted a metal test - which they were awaiting results on - and wanted to do a full analysis.
He said there was no obvious explanation for why the family's water had gone blue, as chlorine was present in around 70 per cent of the country's water, leading staff to believe it could have something to do with the house's water system.
When asked if their reaction had changed because of last month's contamination, he said council would have investigated anyway.