The zero-inflated aspects of the zonal compliance distribution are explained by the existence of a number of water supply zones with a low proportion of properties with lead service pipes. In these zones it may be more cost effective to replace lead service pipes than treat the supply. Also, in the past utilities may have failed to justify treatment for these zones based on their historical lead compliance assessments. Customers with lead service pipes in these areas may be at a considerably higher level of lead risk if treatment has not been put in place. It is important in areas without treatment to establish whether there are properties with lead service pipes and assess their lead risk by other methods of assessment such as lead pipe rig or comparison to supplies with similar water.