HI775 Hanna checker for testing in freshwater applications. The HI775 (Handheld Colorimeter) provides a simple, accurate and cost-effective way to measure alkalinity. Present in varying concentrations in freshwater bodies, alkalinity, from carbonate and noncarbonate salts, provides a buffer against drastic pH changes in water. Used in the drinking water treatment process, the concentration of alkalinity dictates which chemicals are used and at what volumes, as well as protecting finished, potable drinking water in the distribution system. Designed as a more accurate alternative to chemical test kits, the HI775 provides quick, accurate results in a few easy steps.