Unmeasured non-household consumption contributes least to the water balance, as there are only a very small number of non-household properties that are not metered. Distribution system operational use, and water taken legally and illegally make up the minor components of the water balance, contributing 5.7%, and understanding within this area is in need of improvement.
Components that have particularly high levels of uncertainty include water taken legally unbilled, water taken illegally unbilled, and unmeasured consumption. This is due to the high number of assumptions that are used to calculate these values. For example, for unmeasured households a small number of properties are monitored for a period of time then this is applied to all households, thus assuming that they all act the same. This is an inherently inaccurate representation of the population.