I thought I would never drink that much either half of it is just for taking medication/vitamins 3 times daily. My JUG, w/ a straw, is 28oz and to take medication (4 including Hydroxyurea) in the AM takes most of the 1st of 2 refills. The 2nd refill usually mid & late afternoon (with vitamins & another medication) and some times a 3rd refill before bed (w/ medication & for dry mouth at night, ( it last for morning meds the next day usually). Also OJ, 6oz , half-cafe coffee 8oz. It's not hard to intake 64oz of water in a day when you keep it handy during the day. Lot's of visits to the bathroom can be a problem when you're out and about.
I filter my water. So keeping that filled up has to be added to your routine.
In my case I started out with weekly Phlebotomies for 3 months straight, so I made sure I hydrated the day before, day of and day after, so 3 days a week of water intake training came easier for me on the other 4 days.
Hint, I carried my JUG around all day and sipped on it all day between meds. Con: I did to much water a day, I put on water weight.
Everything about PV has a Catch 22 to it. Balance is like, the changing of the waves in the ocean. You go out to meet one and the next one to much & chases you back.

I find drinking a lot of water makes a difference for blood draws and blood pressure. It is difficult to push myself to drink that much.