Edge HP Iron pipe and fittings system is a specially coated cast iron designed for aggressive DWV applications. While Charlotte standard cast iron systems easily meet the needs of the vast majority of DWV installations, in certain aggressive environments, the piping system may need enhanced protection. Charlotte Edge HP Iron is specifically designed for aggressive applications and installations such as exposure to undiluted cleaning chemicals with a pH range of 2 to 12 hospitals, casinos, commercial kitchens, soda fountains, bar sinks and parking garages.