The water meter reading agrees with the bill, so wondering if there was a leak I turned off the main inside the house and noticed that the '0.0001' (one ten-thousandth of a cubic metre) dial on the meter was still rotating slowly. It took 110 seconds to complete one rev, which by my calculations means it would have racked up about 15 cubic metres over the course of the 191 day billing period even with the main inside the house turned off. I did however notice that my neighbour's meter does pretty much the same thing.
Has anybody noticed their meter doing this i.e. is it normal, and what size bills do others get over 6 months?