You'll have to judge your water needs for yourself. I would disagree that we wouldn't recognise the need for water though, any more than there is any trouble knowing when the body needs food again after it's stores are depleted after a complete fast.
How much you drink when you feel thirsty is a matter of choice and learning how your body responds from experience. I started Water Fasting by drinking a 750ml water bottle and then waiting a little and seeing if I was still thirsty, then drinking another and another until that thirst disappeared. But after many days of this I felt distinctly water-logged and my desire for water steadily got less and less. I have changed dramatically since then. I now just take a sip of water when I feel thirsty, then wait at least 10 minutes before having another sip, swishing it around in my mouth before swallowing and making the most of it. This way I only drink what I really need and the desire for water soon goes after a few sips. Whereas if I'd chosen to drink a glass or even half a glass of water it probably would have been too much.