Your body needs 2- 3 liters daily. In winter it can be a little less as there is no water loss from sweating. Bottle that had numbered 5 can be used for carrying water every plastic container or bottle has a recycling symbol. The symbol is a number, ranging from 1 to 7, within a triangle. While you may think nothing of these symbols, they can actually offer a great deal of information regarding the toxic chemicals used in the plastic, how likely the plastic is to leach, how un-bio-degradable the plastic is, and ultimately the safety of the plastic. But you can certainly limit your use of the product. Instead of buying plastic water bottles or other plastic containers, choose glass or invest in a high quality water filtration system to obtain your water from. (this is best for your health anyway).