Re: Why does water in a water bottle taste salty when frozen?

Tommy,

I am assuming that you are using tap water. Tap water contains a lot of 
things besides just water. There are dissolved salts, gases and hopefully 
not too many organic substances.

When water freezes it forms a crystaline lattice that is usually very precise. 
There is not much room for the dissolved salts and other debris so they are
squeezed out. As the ice remelts they will be in higher concentration in the
ice-water mixture and the water may taste different. Also, once excluded 
from the ice which when it melts, may no go back into solution. The gases 
may even dissipate. Alternatively, when water freezes some gasses are 
trapped in the crystaline structure, which it why it expands. 

In any event, when you freeze water and then melt the ice the water is not
the same as it was prior to freezing. At least I hope this is the explanation 
rather than your water bottle growing a culture of some noxious bacteria, 
fungus or algae. You might experiment with distilled water to see if it 
changes also

W. Rich.