In 1972 an independent research team made a survey and found that the Hot Water, "Steam Extraction Method" was superior to all other methods for cleaning carpeting. In 1988, DuPont required that their Stainmaster Carpets must be steam/water extraction cleaned or the warranty is voided.
Currently there are three basic methods of cleaning carpets: Rotary Shampooing, Dry Cleaning, and Hot Water "Steam" Extraction. Each of the first two methods have what appear to be two advantages: shorter drying time and less cost. The major disadvantage is that these two methods only surface clean. While we recommend "Steam" Extraction. This method cleans to the base of the fiber rather than scrubbing dirt deeper into the carpet.
Therefore, for your carpets to be truly clean, the first two methods will require almost monthly (costly) cleanings-compared to annual, or biannual Truck-Mounted Hot Water "Steam" Extraction cleaning.