acutually if you breastfeed/bottle feed your baby with breast milk expressed, there isn't a need to feed your baby with plain water. breast fed babies will not be constipated. it is very normal for baby to not pass motion for more than 3 days. some up to 5 to 7 days. For my baby, ever also up to 4 days without passing motion and we went to the pediatrician. and the pediatrician said is normal and ok one. so no worries. the pediatrician also teaches us tisp to trigger the baby to pass motion, as she indicated that some baby like mine, have lazy guts. But if your baby is older and start eating semi solid food, then you should give some water.