I admit that I'm not well educated on the effect of chlorine on rats, so I can't contribute there. Where I live, we have extremely high quality and frequently tested water. Everyone (humans and pets alike) drink straight from the tap.
With regards to bottle vs. dish, I personally use both. In my DCN, I have three bottles (I prefer the glass ones to plastic ones) and two dishes. The girls like to drink from the bottles, but use the dishes as 'wash basins'.. there's very few things they enjoy more than grooming wish fresh water (it's adorable to watch).
However, they do also enjoy dunking toys in the dishes sometimes, so it's important if you go the dish route that you clean it frequently (I change my dishes twice a day).
With regards to bottle vs. dish, I personally use both. In my DCN, I have three bottles (I prefer the glass ones to plastic ones) and two dishes. The girls like to drink from the bottles, but use the dishes as 'wash basins'.. there's very few things they enjoy more than grooming wish fresh water (it's adorable to watch).
However, they do also enjoy dunking toys in the dishes sometimes, so it's important if you go the dish route that you clean it frequently (I change my dishes twice a day).