I know it's a popular thing at the moment, but there's no scientific basis for drinking a set amount of water each day. Depending on activity levels, moisture content of your food, etc. there's no such thing as generic advise that's meaningful. Your body isn't stupid, just listen to it and drink when you're thirsty. The "you're already dehydrated by the time you feel thirsty" is nonsense for the vast vast majority of people.
Is your urine dark? You aren't drinking enough. Is your urine light or clear? You are. Absent medical conditions and a doctor's advise to the contrary, there is zero reason to make it more complicated then that.
Pretty much nobody in the developed world isn't getting enough salt. Use something like myfitnesspal to track your intake for a bit and see what your sodium levels actually are.