Figure. Legionella colonization of water heaters and point-of-use outlets sampled during 6 rounds of environmental sampling in buildings, San Francisco, California (in rows), by residual disinfectant and sampling interval. Legionella species or serogroups of Legionella pneumophila are represented with different colors. Each row represents a single building and each cell represents the results of Legionella culture for a site within the building. H, water heater; P, point-of-use outlet.