3 liters is around the recommended daily water intake. So if anything you're probably doing better than the average person keeping well hydrated.

It is possible to drink too much water and become over-hydrated, however you need to drink around 20 liters - which honestly sounds incredibly challenging to even do. A lot of the complications from over hydration are due to you now having a diluted amount of sodium/potassium (electrolytes) in your blood stream. Basically your kidneys pee out the excess water, but this takes some of the electrolytes in your blood with it. Electrolyte imbalances mess up all of your organs in various ways.

TLDR; Kidneys and liver can be harmed by over hydration, but 3L of water a day is not anything to worry about