As we discussed, I absolutely have this symptom as well. Have you kept a water log to see how much liquid you are taking in versus putting out? I found it help for me. On average I have a net deficit of 1 liter every day. To clarify, if I take in 4 liters, then I put out 5 liters. I just don't know how the human body can function like that. I have tracked this for over three months, and day after day, I continue to lose water. Keeping a water log takes a small amount of discipline, but if you make a print out for the in log and hang it in the kitchen (add a quick reference chart with the measurements of different glasses and cup that you use) and hang a log in the bathroom...the task becomes easier. Of course I realize for women the task is more difficult.
Do you have constipation or hard stools?
Do you have to use the bathroom frequently?
Do you drink more then 2.5 liters a day?
Do you have high or low blood pressure?
Do you find that you need to use the bathroom 5-15 minutes after drinking something?