Water is the basic element of life, and its quality greatly affects the health of the people, especially the children and the old people. A vital aspect of water quality evaluation is its pH level. Knowing the ideal pH level of water is the key to the health of these age groups. who are still growing and have sensitive immune systems, it is very important to give them water with a pH level that will not hurt them. The pH level of water for children should be between 6.5 and 8.5. The water which is in this range is safe and does not have any harmful effects on their health. In the process of aging, people’s bodies become more vulnerable to dehydration and various health problems. Drinking water with the correct pH level is even more important for older people. The water with a pH level between 7 and 8 is usually good for this age group. The proper hydration levels can prevent urinary tract infections, kidney stones, and other age-related problems.