Denver Water's Assessment of Interior Polyurethane Coating of 108-inch Water Pipeline

Fast set, high solids polyurethane has been used as a coating for the interior and exterior of steel water transmission pipelines since the late 1980s, but it wasn’t until 1999 that the American Water Works Association (AWWA) approved Standard C222 for polyurethane coating of steel pipe and fittings. Over the course of the following decade, the coating system gained wide acceptance for water transmission pipelines among many major water utilities. In 1997, Denver Water installed 8,090 lineal feet of 108-inch diameter steel water pipe with an interior coating of 20 mil thick polyurethane. As this was the utility’s first use of polyurethane, Denver Water has undertaken testing of the pipe polyurethane lining during scheduled shut downs of the pipeline in 1999, 2002, 2006, 2009 and 2011. This paper presents what Denver Water learned from its field inspection and testing program of this early-generation polyurethane lining system. Physical and visual testing has thus far yielded favorable results, proving the integrity of the polyurethane lining after fourteen years of service.