Central Highlands Water will begin fluoridation of the city's water supply from November 16.

The news comes 19 months after the decision to add fluoride to Ballarat water was first announced.

Victoria's chief health officer John Carnie said water fluoridation at one part per million would help prevent tooth decay across all age groups in the local population.

But, he said the move would be of greatest benefit to children.

"In particular, children who live in fluoridated areas of Victoria experience considerably less decay than those in non-fluoridated areas."

He said detailed information had been provided last year to Central Highlands Water customers about water fluoridation.

"In February 2008, departmental officers held community information sessions to give residents the opportunity to ask a panel of experts questions about water fluoridation."

Western Victoria MLC Peter Kavanagh said the move was scientifically misguided and a serious error.

"People should be required to gain approval at a plebiscite of affected people before adding fluoride to their water supplies," Mr Kavanagh said.

"Although fluoridated toothpaste is very good for teeth, scientific studies show that any benefits from drinking fluoridated water are very marginal, but the potential harm to human health from swallowing fluoride is significant," he said.

Ballarat Health Services population health and strategic planning manager Tracey Wilson, said science was on the side of fluoridation.

"There's an overwhelming breadth of research showing that fluoride at one part per million is safe."

She said fluoride was the last piece of the puzzle for improving dental health in the region. The change will affect all Ballarat suburbs, as well as surrounding towns connected to the city's water supply system.