Water can kill you if you drink too much of it.
There's what is known as water poisoning where your kidneys cannot get rid of the water fast enough and so the water then becomes toxic to you.
However to get water poisoning you would have to drink a few gallons of water in an hour and continue to do so throughout the day.
So if you drank 5 to 10 gallons of water per day then it could lead to water poisoning.
But drinking 1 gallon to 2 gallons of water per day should not be harmful depending on your body weight.
But 1 gallon of water or at least 1/2 gallon of water per day is usually enough to keep you healthy and keep your kidneys healthy.
There's no requirement to drinking a gallon of water per day to stay healthy.
However if you want to drink a gallon of water everyday to stay healthy you certainly can as 1 gallon of water per day will keep your kidneys flushed and help prevent bladder infections, kidney disease, kidney stones etc.
Always drink water or other hydrating drinks before you get thirsty to prevent dehydration.
As long as you're drinking 1 or 2 glasses of water per day or a few bottles of water per day and drinking other healthy drinks you'll be okay.
To stay healthy you're supposed to drink at least 8 glasses of water or even 1 gallon of water per day.
However you don't have to drink 1 gallon of water everyday or even 8 glasses of water everyday.
As long as you're drinking 1 or 2 glasses of water or a few bottles of water per day you'll still keep healthy.