Which of the following is NOT a common method for treating potable water?

Steeping is not considered a common method for treating potable water. In water treatment, the primary goal is to remove impurities and pathogens to make water safe and drinkable. The other methods listed—filtration, flocculation, and chlorination—are standard processes that play essential roles in the treatment of potable water.

Filtration involves passing water through various materials to remove particulates and microorganisms. Flocculation is a process where chemicals called flocculants are added to water to bind small particles into larger aggregates, making it easier to remove them from the water. Chlorination is a disinfection process where chlorine or chlorine compounds are added to eliminate harmful bacteria and other pathogens.

While steeping may be associated with other processes such as brewing or extracting flavors, it does not serve the purpose of purifying water for drinking. Thus, it is the method that stands out as unfamiliar in the context of conventional potable water treatment practices.