This research explains one of rason why yerba mate washes away quickly. Yerba mate undergoes some physicochemical changes it tends to lose its "organoleptic" properties, that would trigger its washing, caused by the lixiviation of its components. While we were making the research, 882 experiment were conducted and 9,702 mates were brewed. A higher frequency of quickly washed mates was observed when using water with pH 6.5 and a lower frequency of quick washed mates when using water with pH 8.5. Our results suggest that pH significantly influences fast washing of yerba mate; lower pH allowed of drinking water, the faster yerba mate is washed regardless of the temperature used. Chi-squared test demostrarte the causal relationship between fast washing of yerba mate and drinking water pH. t-Student test showed that yerba is washed fast using water with a slightly acidic pH.