Water helps prevent the formation of kidney stones and urinary tract infection. Drinking a lot of water helps produce much urine which in turn helps flush out infection causing bacteria from the urinary tract.
It is unlikely that drinking too much water will harm or damaged the kidney, but in rare cases, drinking a lot of water within a short time can be dangerous to the body, when the kidney can excrete the excess water, the sodium (salt) content in the blood gets diluted which causes a condition known as HYPONATREMIA which is harmful and can be life threatening.