I'd always suspected it was a bit wasteful to keep buying bottled water instead of refilling a bottle - even a 'disposable' one - with tap water several times.
This article at Smithsonian magazine online is an eye opener.
You don't realise how much extra water goes into making that bottle of water for you or how much energy is consumed both in making the bottle and transporting it to you. The reality is, most tap water is fine to drink and it actually doesn't taste much different, particularly if it's cooler than room temperature (pop an ice cube in there). The key to reusing any bottle is to wash it out with warm, mildly soapy water regularly - if not everyday - and let it dry out completely.