Opened Mineral Water bottles

[WendyS]

How long can we safely keep an opened half-used mineral water bottle after resealing it? Tend to buy the 5 litre containers so they last awhile but am equally interested in the safety aspect of smaller containers once opened.

[Bob04]

I drink 2 litre bottled water (plastic bottle) which I read is supposed to be drunk within 4-5 days of opening. The furthest I have gone with the same bottle is about 10 days (I'm still alive). I have noticed a different odour from the water if left for more than a week though.