Even plastic pipes can produce impurities and contamination. So, you decide the safest course is to use bottled water. Bottled water comes in many kinds, and must be clearly labled. It is usually classified as to its source type, spring, spa, glacier, public water supply etc. There can be a lot of confusion and overlapping in these labels, there are no rules in place to govern appropriate labeling, so some claims may be misleading or incorrect.
Mineral water is natural spring water.
The word natural on the bottle only means that the mineral content of the water has not been altered from its original state. Make sure you check that bottles labeled Natural spring water list the water source on the bottle. In addition to containing minerals, the water must flow freely from its source, it cannot be pumped or forced from the ground and must be bottled directly at the source. You need to be aware of the minerals in the water you choose to drink. If you drink mineral water for therapeutic reasons, and the water you drink contains minerals your system doesn't require, you could be doing yourself more harm than good.