I know that when I used to take Urva ursi (kidney cleanse), I used to need to rush to the bathroom in order to prevent accidents and this was definitely due to the toxicity of the urine, not the amount for I would not pee that much.
However, if you lack electrolytes, the water is going to go right through you with being assimilated even. And you will pee plenty.
It is obvious that the kidneys are intoxicated and need to get rid of extra toxins, and therefore it is quite normal to drink plenty and pee plenty. I used to drink 4 liters of water a day. (And most likely pee just as much).
In order to make sure water does not just pass through you, a dash of lemon juice into your dink will insure the presence of electrolytest that help with assimilation of water.