If the final vacuuming operation is not thorough, some of the powder will be left in the carpet pile. With repeated cleanings, enough cleaning compound can accumulate to cause some discoloration by its own presence. It can, at best, merely postpone the need or reduce the frequency of professional cleanings. Rental units lack adequate power, and consumers usually lack the expertise to succeed in properly maintaining carpet and prolonging its attractive life. There is no magical, single method for carpet cleaning.
All methods have advantages as well as disadvantages.
Moreover, different people can achieve different results while cleaning the same carpet with identical equipment. No method can compensate for an inept operator. Therefore, it is more important to select the right cleaner than the right cleaning method. Not all cleaners are alike. In fact, the difference in the quality of service from one cleaner to another can be astounding.