Is there a way to determine the volume of water to be consumed during a fast?
The general rule is to drink when you’re thirsty. If you want a number, anything between 1 and 2 litres a day depending in how much you’re sweating out during the day.
A lot of the water your body needs is connected with digestion, which isn’t happening as much in a fast (depending on the duration). The more water you drink the more of your body’s salts will be used, so too much is bad. However, you need more water than usual to flush your kidneys and prevent kidney stones (especially on extended fasts) as fasting tends to release more fat soluble toxins.
It’s important to drink sufficient water. Depending on activity, you could need at least two litters. The body is still removing toxins, and you need water to protect your kidneys from damage. Be sure to stay on top of your electrolytes, failure to do so could result in an ambulance ride to the ER.