In fact, one company that’s been put to the test – Nature’s Best – was found to be really not that different to tap water at all.
Australian tap water is subject to stringent testing and regulations to ensure it’s safe to drink but bottled water is classified as a food product and not subject to the same controls which means quality and mineral content can vary depending on the brand.
Testing showed tap water has a relatively high concentration of minerals like calcium and magnesium, more than most of the bottled brands, except Fiji water.
"Below four is something that does damage your enamel," Dr Leusch said.
"Tap water should really be marketed as mineral water."
Dr Leusch said anything that said "safe, pure Australian water" was probably just tap water.
"In the end, I reckon when you’re buying this, most of the cost is the plastic container.
Gold Coast tap water had a level of fluoride that was expected, but all bottles contained some amount of it, and Nature’s Best had more.
"It’s a natural element, it’s found in some of our groundwaters as well," Dr Leusch said.
Pure water is more generic than that and it can actually be tap water that has been filtered and bottled into this."