First of all, if you are doing the super low carb diet thing (atkins), you need to get better educated. Fiber doesn't count as a carb. In fact, if you eat something with 20g carbs total and 10g fiber, you only count 10g.
LOL. I'm not constipated at all. And yes I do drink over a gallon of water a day. I would say like a gallon and a half. It's just that since I started this low carb diet, I've been only poopin once a day. When before I would go 3-5 times a day.
hehe, well.. enough for what? what is your purpose for using fiber, it's not really essential for life, but it can be useful for a number of reasons... so it really depends on your reason.