At what point do you need to carry water on the run (Page 2)

I coach a weeknight 'short' run.. up to 11 miles generally, for a local club, and i make carrying 'hydration'.. water, or whatever you prefer, mandatory no matter the distance, if it's over 80 degrees. If it's under, then I let the runner decide. Generally, 90 percent of them carry it no matter what the temps. Of note, is that we get 20+ runners, and out of those, maybe one or two use a fuel belt, or belt of any kind. Most just carry a bottle in their hands.

Bottom line is it's just a good habit to have. Get used to carrying it, and don't worry about the 'point' you need to carry it on the run. I even carry some on 3 mile runs. Don't drink much, but have it with me at all times just in case.

I only carry 16oz throw away water bottles. They are the perfect size and nice and narrow.

Here's a fluid intake needs calculator from the Gatorade Sports Science Institute.  Obviously they have an incentive to have you take in more fluids, but they do have a statement on there warning you not to overhydrate.

http://www.gssiweb.com/FluidLoss.aspx

Here's a link to a study (excerpt) regarding fluid loss and performance deterioration:
http://www.humankinetics.com/excerpts/excerpts/dehydration-and-its-effects-on-performance

Great post.  I'm training for a 10K and was wondering the same thing.  I've never carried water up to 4 miles, but wondered at what point I might need to. 

Seems if I do carry water, there would be no need for a belt with more than two bottles.