Carpet Cleaning: Not as simple as all that
Carpet can hold many times its own weight in loose dirt. It works like a filter of sorts, catching anything heavy enough to land on it, weather you can see it or not. The things that land in and stay in your carpet, can behave like a nail against fiberglass, scratching and permanently damaging the fibers.
The best way to avoid this damage, is very thorough vacuuming of your carpets, several times a week, depending on traffic and use. Use a good quality vacuum, with a HEPA-type filter or bag. Making several passes, slowly, in one direction, and changing direction doing the same, will assure the most dirt removal.
When your carpets becomes dingy or stained, your best bet is to hire a professional carpet cleaner, preferably IICRC (Institute of Inspection, Cleaning and Restoration Certification) certified, to clean them. There are a few different methods of professional cleaning, all of them good ones, depending on the extent of cleaning needed.
For very dirty carpets, HWE (hot water extraction) can be the best method for cleaning your carpets. As long as the PSI (pressure per square inch) of the machine used is not too strong, the flooring under the padding will not be damaged. Carpet cleaners use a "CHAT" scale , using many variables to thoroughly clean the carpets. "CHAT" consists of chemicals, heat, agitation, and time.
Your carpet cleaner will first vacuum. This is a must. Next, he or she will spray on a chemical called a Pre-Spray, and allow it to stand for about 5-20 minutes, depending on the depth and content of the soil. Then they will use a rinse with their truck mounted or portable carpet cleaning machine. They will spray the solution with a "wand", and take several dry strokes with the wand to extract excess liquid.
Many cleaning chemicals have a level PH and will not damage your carpet or the flooring underneath. When a higher PH level is necessary due to deeper soils such as pet urine, etc., a more acidic chemical known as an "acid rinse" is necessary to equalize the PH in order to avoid the "glue for dirt" that higher PH chemicals can cause. You will also want to make sure your cleaner uses air movers (high powered professional fans) to aid in the quick drying of your carpets. Anything over 12 hours for a drying time is really too long and can cause mold spore growth with in 72 hours.
The problem with most of the over-the-counter carpet cleaning chemicals is that they are very high PH (if the label says anything over a "7" PH, it is going to be too much), and can "bleach" color out of your carpet and leave lighter spots that can not be remedied without carpet "dying" (done by a pro, of course).
For lightly soiled, newer carpets, a VLM (very low moisture) process can be used. For this process, a very low PH chemical will be applied after thorough vacuuming. This chemical will be allowed to stand for a few minutes, and then the cleaner will use a rotary machine with a "bonnet" attached to pull out the soil. The bonnet is a loosely looped "mop" like attachment, which will pull lighter soil out by using a circular motion. This can be very effective for lightly soiled, newer carpets, and if this method is used on a regular basis, can add years of life to your new carpet.
"Spot" cleaning is not necessary when using a professional cleaner, as he or she using the "pre-spray" will have very good results. If additional stain removal is needed, it will be done after the initial cleaning, using special chemicals made especially for certain types of stains, a "tamping" process (the cleaner will use a white towel and a flat brush to hit the stain under the towelthis process pulls the soil into the towel), with extra rinsing after that.
If you take this advise, and have your carpets professionally cleaned regularly (at least every 6 months; more often if you have heavy traffic), your carpet will last for much longer than it will if you only vacuum occasionally, saving you hundreds or thousands of dollars over the course of your carpet's life.