The main objective of this research was to provide information to the rainwater harvesting community in Texas regarding the impact of roofing material on harvested rainwater quality. In this study, five pilot-scale roofs (asphalt fiberglass shingle, Galvalume metal, concrete tile, cool, and green) and three full-scale residential roofs (two asphalt fiberglass shingle and one Galvalume metal) were equipped with rainwater sampling devices to collect the “first flush” and water after the first flush. The harvested rainwater was collected from multiple rain events and analyzed for the following parameters: pH, conductivity, turbidity, total suspended solids (TSS), total coliform (TC), fecal coliform (FC), nitrate, nitrite, total organic carbon (TOC), dissolved organic carbon (DOC), selected synthetic organic compounds, and selected metals. While metal and tile roofs are commonly used for rainwater harvesting in developed countries, our limited data set suggests that asphalt fiberglass shingle and cool roofs also might be considered for this purpose given the quality of harvested rainwater that they produced; additional studies of asphalt fiberglass shingle and cool roofs are needed to provide a robust data set on harvested water quality.

Michael Barrett (University of Texas at Austin), Mary Jo Kirisits (University of Texas at Austin)

Mendez, Caroline, Afshan, Brigit, Kinney, Kerry, Barrett, Michael,  Kirisits, Mary Jo. (2010) Effect of Roof Material on Water Quality for Rainwater Harvesting Systems.  Report for the Texas Water Development Board.  January 2010.