Yes drinking lots of water is great for your kidneys and helps to flush toxins out of your kidneys and bladder to keep kidney disease, kidney stones and bladder infections away.
Water is the best drink to stay healthy and hydrated and you should drink water even when you're feeling thirsty and your body and kidneys will be much healthier as a result.
Just don't drink too much water as you can get water poisoning but drinking 8 glasses or 10 glasses of water per day is perfectly fine.
I drink at least 5 glasses of water minimum per day but during the summer I sometimes drink up to 8 glasses of water if I'm feeling really thirsty.
You can also drink some apple cider vinegar to help flush toxins out of your kidneys and keep them healthy as well or other natural fruit juices.