Here's the case that makes me cringe: I know some families that don't think their tap water is clean enough to drink, and they reuse disposable plastic bottles

Here's the case that makes me cringe: I know some families that don't think their tap water is clean enough to drink, and they reuse disposable plastic bottles for months to store spring water that the whole household drinks. That can't be good long term. In your situation it's probably not worth stressing too much if your plastic bottle is built to be reusable or if it's not your primary source of water. It's difficult to find reliable data on this, partially because how bad is the least durable kind of plastic legally allowed for drink containers depends on local (and changing) regulations. In presence of such uncertainty, personally for myself and loved ones I apply the following reasoning: – If bottle’s plastic is thin and easily crumples, routine handling and refilling will cause plastic surface to degrade and microscopic cracks will make chemicals from the container more likely to seep into water. – There is a well-publicized experiment from last year that found varying amounts of microplastics in newly purchased water bottled in plastic; I find it likely that after reusing a plastic container not designed to be reusable the amount of microplastics would only grow. – Glass bottles are great!