On a lot of bottles of so called mineral water, it is advised not to refill the bottle (with ordinary tap water, or any other drink e.g. cola) as doing so may present a health hazard. Is there any evidence behind this warning, or is it simply companies trying to get you to buy more bottles of water?
The University of Calgary study referenced here only has the possible build up of bacteria as a risk, and even that is avoidable if the bottles are washed between uses and occasionally something stronger such as bleach is used.
The same link also discusses the other myths around dioxins and pthalates leaching from the plastic to the water, and the original paper on that is available here.