There is also water toxicity and can be just as dangerous as anything else toxic, but as long as you spead the water consumption over the day that should not be too much. The only caution is trying to "force feed" water drinking like a gallon or two in 30 minutes or something, but if you do this all the time and take a multivitamin so that you don't deplete your resources...you should be fine.

On a lighter note - how much time do spend in the bathroom?!?!? =)