The purpose of this research was to evaluate the need to repeatedly sample water from homes to identify infrequent, but high "spikes" in water lead levels due to the sporadic release of lead particulates. The Illinois and Pennsylvania data were used in establishing baseline (first round of sampling) water lead levels. The simulations were created using various assumptions of baseline prevalence and various probabilities of spike occurrence on the N+1 round of sampling, given the results on the N round.

The findings of the research indicate that household tap water needs to be sampled at least 5–7 times to achieve a 50% probability of identifying hazardous spikes in water lead levels.

The Illinois Lead and Copper Rule dataset was downloaded from http://163.191.83.31/dww/index.jsp for 2020 and the first half of 2021. It excludes water samples from source water and from water upstream of home/school sampling points.

The Pennsylvania Lead and Copper Rule dataset for 2020 and the first half of 2021 were downloaded from http://www.drinkingwater.state.pa.us/. That dataset includes water samples from source water and water upstream of the home/school sampling points.

The code was used to simulate water lead levels in 100,000 homes each sampled 15 times, under a variety of assumptions about baseline distribution of water lead levels and transitional probabilities. The tables are the output of that code.