Carpeting is a soft and warm flooring option, but it’s the hardest material to clean because it’s made from fibers that trap dirt and soils. Carpet manufacturers recommend you clean carpets periodically with a shampooer or steamer. The best method to use depends on the level of clean you want to achieve. For example, while both will make your carpet brighter, shampooers sometimes leave dirt behind.

How Shampooers Clean

Shampooers use warm water mixed with soap to create a solution that the shampooer applies to the carpet. It then removes the dirty solution after it dries. Shampooers typically spray a shampoo and water solution or a dry foam onto the carpet. A revolving or rotary brush then works the shampoo or foam into the fibers to loosen the dirt. Sometimes this process can overwet the carpet, which prolongs drying times, and the brush can damage delicate carpet fibers.

How Steamers Clean

Steamers use warm to hot water to loosen dirt in your carpet, and then they extract the dirt from the fibers with a powerful vacuum and carry it to a holding tank. While the name “steamer” implies your carpet is being cleaned with steam, a steamer actually uses warm to hot water to clean the carpet. A spray of water is used to force the dirt from the carpet fibers, and a vacuum located in front of the spray immediately sucks it up. Carpet steamers are typically similar in design, but the temperature of the water used varies. Some machines use cold water that is heated to boiling water. With steamers that heat to extremely high temperatures, there is the risk of scalding if the water line breaks.

Level of Cleaning

Shampooers are a surface cleaner, which means they clean the upper portions of the carpet fibers but may not reach dirt and residue that settle to the bottom. Steam cleaners provide deeper cleaning, extracting with enough force to pull the dirt from the bottom of the carpet fibers. Shampooers basically bury the dirt in foam and often have brighteners that make your carpet look cleaner than it really is. Eventually this can lead to yellowing, which can’t be removed.

Cleaning Frequency and Timing

Carpets should be shampooed or steamed every 12 to 18 months. The frequency depends on the quality of your carpet, how much traffic it receives and whether or not you have pets. For example, a carpet in a guest room doesn’t require cleaning as often as one in a family room, and a carpet in a home with pets may need more frequent cleaning than one in a home without pets. Your timing is also important. It’s best to steam or shampoo your carpet before it gets too dirty. This is most important when using a shampooer, however, because you don’t get a deep clean. This means if you wait too long to shampoo the carpet, dirt and soils settle where they may remain even after shampooing.

Source - https://homeguides.sfgate.com/shampooers-vs-steamers-91224.html