This is a common question we get all the time and I will try and explain the different techniques and the benefits and disadvantages of each. First you have the rental or store bought type of equipment which would fall into the portable carpet steam cleaning category. Now these for obvious reasons may be one of the worst choices for carpet cleaning do to be so underpowered they are not able to properly rinse or recover any of your cleaning solution which will cause rapid resoling. Believe me if those little machines worked well us professional would not spend twenty thousand dollars on just our machine alone.
Ok, then you have dry cleaning or bonnet cleaning which uses a dry cotton pad typically to buff if you will the carpet in hopes of transferring the loosened dirt to the pad itself. Not very effective and since there is no rinse of the carpet pile lots of cleaning residue is left to rapidly re-soil just like the do it your self machines.
Then you have truck mounted steam cleaning equipment which are powerful gasoline engines mounted inside the vans or box trucks. These are state of the art equipment that create unrivaled vacuum and heated water like nothing else in our industry. Not to mention this process is the preferred method of the world largest carpet manufacturer. When proper steps are taking this is by far and away the most thorough longest lasting clean in the industry. Simply put a pre vacuuming is done, then a pre treatment cleaner is applied and lightly agitated into the carpet pile, then a very thorough and hot rinse is done, and finally a very strong vacuum extracts all the contaminants and cleaning residue as well as the water from the carpet. This will leave you with a fresh and soft feeling carpet free of everything you wanted out of it as well as free of cleaning residue so many others leave. This is the process my company uses exclusively and our clients love it!