I don't think you should pay for the bill since you were not using the house then. The previous owner should instead clear the bill he/she left behind. If this matter gets too complicated, you can contact your lawyer for professional help.
no you are not. you start paying for the bills from the date the keys were handed to you. you can get legal aid if some one is pressing you to pay. i was in this situation and actually ended up getting compensation
No talk to your landlord if for some strange reason he refuses to pay what he should get it in writing that you too will leave the final water bill unpaid when you move. That should make him think as you could run up a huge bill. He needs to pay it to keep the water on.