Tenants did not inform about running toilet, huge utility bill

[Calvin D.]

I have some young tenants in a main floor of a house. They are respectful and nice, but did not think to inform me that the toilet was running all the time, though they noticed it was “always making noises.” I just received a $900 water bill for last month, which is how I found out about this. If I had known about the running toilet I would have dealt with it immediately. Who is responsible for this water bill? Thank you!