Only 70 per cent of bottled water and drinking water from vending machines has passed quality standards set by the Department of Health, director-general Dr Somyos Deerasamee said Wednesday.
"The problem lies with contamination. Contaminants include heavy metals and bacteria," he said.
Contaminated water causes various diseases including diarrhoea and typhoid, he said.
Only 40 per cent of water from waterutility services, artesian wells, rain and shallow wells passed the department's quality requirements, he said.