Given that humans, along with all other organisms, are largely made of water and need to drink significant amounts every day in order to remain healthy, the answer to the question of the healthiest type is of utmost importance. One of the questions raised is about the safety of tap water vs filtered water, the answer to which has been quite confused by marketing campaigns and other media trying to sell their point of view.
Marketing campaigns are not all bad. Thanks to them, many people have learned in the recent past that bottled drinks are bad for the environment. All those bottles require oil to produce the plastic they are made out of, and most bottles are not recycled but instead sit in landfills for the many years required for plastic to biodegrade. Even those that are recycled require energy to be turned into new products. So, environmentally speaking, bottled is not the best choice.
What people don't always know is that standards for bottled water are actually not as stringent as those for city tap. In the US, the testing rates required are actually lower, even for things like bacteria and toxic heavy metals. This means that bottled, which is largely sold as a healthier alternative to tap, may not be safer than tap.
Studies done in the US have shown that while some bottled brands tested safe, others show chemical, heavy metal, and bacterial contamination. Given that the study is just a snapshot in time of bottled water brands, this result means that all brands must be viewed with suspicion. The idea that bottled is safer than tap is just not true.
People who are concerned with the disadvantages of both bottled and tap waters often turn to filtration devices. This can be purchased from an outside company that then sells it to customers in large bottles, or it can be an in-home filtration system. In-home systems are both cheaper and the more ecologically friendly choice, though.
Many large brands of bottled drinks actually provide filtered tap, not spring water or other 'naturally sourced' types. Given that the bottles are bad for the environment and purchasing them is expensive, using a home filtration system makes sense. Water from a filtration system is essentially the same as many types of bottled.
Using an in-home filtration system will allow you to get the best of both worlds-- the tap that you purify will be held to the high municipal standards required by the overseeing agency, but your purification device will remove any remaining contaminants. If you do not wish to drink the chlorine, chloramine or fluoride in tap, using a purification device can remove it.
The question of tap water vs filtered water is largely a matter of personal preference. Bottled is expensive and ecologically, a poor choice. But personal, in-home filtration systems are both economical and very effective. However, since tap is held to very high standards, most authorities do not think that additionally purifying it is necessary.