How much water should our 15 month olds be drinking?

Michelle • 26. Momma to Grayson 01.23.17 and Archer 11.21.18 💕

How much is normal for our 15 month olds to be drinking of water? I always have a soppy cup of water available to my son and he seems to be always drinking. I sometimes have to fill it up 3/4 times a day cause he drinks it so fast and gets so mad when it’s gone. He still has 2 bottles of milk a day (16 oz averagely).