There are three (3) ways by which your Plan’s water usage charges can increase:
1) a change to the charging parameters
2) an increase in usage charges
3) an increase in water consumption.
Most Water Utilities (in NSW) recently made changes to items (1) and (2) by in the first instance replacing a stepped tariff where consumers paid one price for each kilolitre (kL) used up to a threshold and a higher price for each kL used above that threshold, to a flat-rate tariff for the lot, and in the second instance by increasing the amount of that flat-rate tariff.
Your Plan’s Water Account should incorporate a graph that shows the average daily consumption for the current and past billing periods, so check for a real increase in the water usage as opposed to an increase in the invoiced charges.
You may find that your Plan’s water usage hasn’t increased, or if it has, the amount of any usage increase (kL/d) may be much less than the invoiced increase ($).