The tall and narrow tank of the Viper 1.28 gpf toilet optimizes flush speed, and quickly refills using the industry-best Fluidmaster 400A Fill Valve, the company says. Large, dual-fed siphon jets increase flush speed, for a quick and clean bowl every time. An exclusive multi-point mounting system ensures long lasting stability and ease of tool-free installation. Gerber’s Viper is WaterSense-certified and is a High Efficiency Toilet (HET), saving 20% more water (versus a 1.6 gpf toilet) and money, while also featuring a drain line carry of at least 50 feet and MaP score of 1,000 grams, the company notes. Gerber.