I believe this is the 3-tier system Rubicon refers to:
Ex.: for NORTH SUMTER COUNTY UTILITY DEPENDENT DISTRICT
Use rate - per 1,000 gallons
First 4,000 gallons..........$1.72
4,001 - 8,000 gallons......$2.88
8,001 and up ................$4.01
See also
Village Community Development Districts
Bill