It is all contingent on the specifics in the lease; however, the law in the majority of states clearly states that the landlord is ultimately responsible for all repairs and/or additional expenses incurred as a result of the damage that occurred from the tenants use, (and here's where it gets sticky), as long as it has been determinded that the tenant exercised reasonable care when operating the device or apparatus under normal circumstances. Can you say "law suit" :))))))
Whoever is paying the bill currently. If the landlord is paying the bill, and the bill is figured into your rent, then the landlord will pay the bill. However if you are responsible for the water bills then you are going to be the oneresponsible to pay the bill.
The person who is currently paying the water bill is responsible for paying the water bills regardless of the problem. When a problem is found out, the tenant is supposed to let the landlord know that is it fixed as soon as possible to avoid bills caused by damage.