Vacuuming alone won't protect your carpet. Even though vacuuming can remove most soil, it is also necessary to clean your carpet on a regular basis to remove the oily, sticky soil that vacuums don't remove. These soils result from cooking vapors, air pollution, and tracked-in dirt from outside. The particles of oily soil deposited on carpet fibers can cause gradual but significant dulling of colors. The color isn't lost, but is hidden under the film. If this type of soil is allowed to accumulate, it begins to attract and hold the dry soil. If carpet is cleaned before it becomes too unsightly, the cleaning chore will be easier and more successful.

Carpet in a typical household should be cleaned every 12 to 18 months, depending on the number of residents and amount of activity. Choosing the proper cleaning system is important. Some systems may leave residues which accelerates re-soiling and defeats the whole purpose of cleaning. The recommendations below represent the best current knowledge and should help prolong the time between cleanings.
What cleaning system should you use?

Shaw Industries recommends the hot water extraction system.

Research indicates that the hot water extraction system provides the best capability for cleaning. This system is commonly referred to as "steam cleaning," although no steam is actually generated. The process consists of spraying a solution of water and detergent into the carpet pile and recovering the water and soil with a powerful vacuum into a holding tank. This can be done from a truck-mounted unit.