'Whenever you disregard your sense of thirst and strive to ingest several glasses of water a day just because you have been told that doing so is good for your health, you actually put unnecessary strain on your body in two major ways:

Ingesting more water than you need can increase your total blood volume. And since your blood volume exists within a closed system (your circulatory system), needlessly increasing your blood volume on a regular basis puts unnecessary burden on your heart and blood vessels.

Your kidneys must work overtime to filter excess water out of your circulatory system. Your kidneys are not the equivalent of a pair of plumbing pipes whereby the more water you flush through your kidneys, the cleaner they become; rather, the filtration system that exists in your kidneys is composed in part by a series of specialized capillary beds called glomeruli. Your glomeruli can get damaged by unnecessary wear and tear over time, and drowning your system with large amounts of water is one of many potential causes of said damage.'