What are the methods for purifying the three types of impurities (moderate, severe, and less than that), and are some of these methods compatible with others, and what is the criterion for each?

An impure object is purified by washing it with pure water until the water separating from it is pure and unchanged by the impurity, and the taste, color, and smell of the impurity are removed. However, if the removal of the color and smell is difficult, they are excused. As for minor impurities that are pardoned due to their small quantity or difficulty, they do not require washing. This includes an amount of blood, pus, or serous fluid equivalent to the size of a dirham.