Although Harrison water customers will pay 5 percent more for service per year over the next six years, starting in January, the overall increase comes to about 34 percent, not 25 percent because each increase is based on the previous year, which shows an increasingly larger amount.

The sample presented by engineering consultant Arcadis may not be realistic, but here’s how it works. A 2012 monthly water bill of $25.10 will increase this way:  $26.36; $27.67; $29.06; $30.51; $32.03 and $33.64.