Food containers typically use non-recycled plastics to prevent contamination and to maintain a known composition for the bottle. Water is a food product and recycled material is too expensive when purified to the level needed. This means every bottle started from oil extracted from the ground.
But even starting with chemically pure PET doesn’t stop all the problems. Various chemicals are added to the plastic and the manufacturing process can introduce even more. Any or all of these have the possibility of leeching into the water the bottle will hold. ...
Since only about 25% of plastic water bottles are recycled, one cost is disposal. With about 50 billion bottles sold in the US yearly, this is no small issue. Another economic problem is transportation.
Compared to tap water (which has its own problems) bottled water needs to be packaged, stored, moved (sometimes hundreds or thousands of miles from the source), refrigerated and transported again by the consumer.