WHY DOES MY WATER BILL VARY? This is a very good question. It seems like if the bill is monthly, it should be the same each month, right? Well, Greater Cincinnati Water Works bills according to a billing cycle, and the cycles are not the same. One cycle may have 24 days in it, while another cycle may have 34 days in it. So the rates are calculated as daily rates, then multiplied by the number of days in the cycle. Additionally, since Greater Cincinnati Water Works collects the waste and recycling fees as well, those monthly rates are calculated the same way.
Now you know why your bill varies from month to month!
Original source can be found here.