hi -
with water bills (if you are not on a meter). you pay for the water, based on the value of your home (NOT how much water you use). this is known as rateable value water charging.
like on you council tax, it goes from band A to F and depending on your house/area - the more/less you pay.
i.e = in me old house, the water was �182 a year, and the council tax was band A = �900 a year or close to that.
now i moved house, i have gone to council tax band d = �1500 a year, and the water is apparently now on a meter, and we got an estimated bill for the next year of �351.00. as according to the water board it goes off how many people live at the house (there 2 of us), and we only moved in two weeks ago! but was assured by the water board, that the meter was read two weeks before we moved in (and at that time the house was empty leading up tp us moving in (sparing a few painters). also the water board are saying that water meters are now compulsory, oncer there installed they stay.
best bet is to read the back of your bill