Why is it OK to drink from a disposable plastic water bottle but not to refill it with water and drink from it again? The plastics in question differ, but in general, concerns involve a combination of bacterial contamination and the leakage of chemical compounds. In theory, it would be safe to clean a bottle carefully and reuse it, but in practice, it doesn’t work that way. The bottles are designed to be disposable, so they’re flimsy, and when you wash them well enough to get rid of the bacteria you introduce by drinking from them, they are easy to damage slightly, especially if you do this repeatedly. This causes imperceptible cracks where bacteria can accumulate and chemicals may be released.
Anyway, if you think it’s environmentally wrong to discard all those plastic bottles after using them only once, why buy that first bottle if you’re simply going to refill it with tap water? Instead, buy a refillable container (stainless steel, certain stable plastics, glass with a protective frame, etc.), which can be washed and reused repeatedly. These words follow a rule: