Changes in Water Quality in Premise Plumbing: Cold Water vs. Hot Water

摘要

In recent years there has been increasing interest in the quality of water in premiseplumbing, which drinking water regulations are not designed to address. The Safe DrinkingWater Act focuses on the distribution system although the Lead and Copper Rule addresses theeffect of distribution water on plumbing materials. NSF standards and plumbing codes coverplumbing materials and construction. The National Academy of Sciences, however, identifiedpremise plumbing as a priority area for research to reduce public health risk for several reasons:high surface-to-area ratio of piping; low or no disinfectant residual due to buildings being 'deadend'in nature; higher likelihood of cross connections due to installations done by inexperiencedor unlicensed plumbers; and likelihood of bacterial regrowth (particularly Legionella). Recentstudies on the exposure of humans to DBPs during bathing and showering also highlight the needfor a better understanding of changes in water quality in residential plumbing systems.The Philadelphia Water Department (PWD) studied the effects of residential plumbing onvarious water quality parameters: temperature, chlorine residual, ammonia, pH, heterotrophicplate count, total organic carbon, and disinfection by-products (TTHM and HAA5). Volunteersfrom throughout Philadelphia sampled their homes' cold and hot waters. For two seasons,significant changes in many of the parameters were seen between cold and hot waters: chlorineresidual decreased, ammonia residual increased, pH was largely unchanged, HPC counts varied,TOC was unchanged, TTHM increased, and HAA5 increased. It seemed that the magnitude ofthe change between hot and cold water temperature may be an indication of the change in waterquality. The changes were somewhat unique by household and this raises the question of certainconsumers being more impacted by water quality changes that are not otherwise indicated bycurrent monitoring programs. Recommendations will be made for researchers to conduct bettersurveys of water quality changes in premise plumbing as more research is pursued on this topic.