Originally Posted by
Calsun
Two water bottles will be more than enough if you start the ride well hydrated.
Agreed, with the caveat that you refill those two water bottles every chance you get -- at least every couple hours -- and drink. Water in bottles does a rider no good, water that's been drunk does a body good.
I'm mostly agreeing because I'm being picky about wording. Someone who's riding at the 15 mph mentioned above for seven hours probably needs more than two bottles of water. And of course that depends on reasonable spacing of rest stops; 3 hours between stops ending with an hour's climb will be problematic.