re: What can apartment communities/landlords be responsible for?

I'd imagine there is no way the landlord will pay the water bill for you. It is in your name and utilities are your obligation. Just be glad you caught it and are getting it fixed. I would only complain/demand money if it takes the landlord months to fix it and you continue to have to pay the huge water bill for multiple months.

ETA: May want to turn off the water to the toilet to avoid this if you haven't already. I assume that's possible.