I've been using this stuff for a number of years. It does an amazing job of getting my carpets nice and clean. I'll get a stain on it and it won't get cleaned for quite some time until I'm ready to clean the carpets and it comes right out. On really good stains, I'll shoot out a little extra cleaner onto the stain and let it soak in a couple minutes and then go over it. My Carpets almost look NEW even though they aren't. I'm seeing some of these other pictures and the carpets are nasty. I would never let my carpets get in that condition. I'd be embarrassed for anyone coming over and seeing that.
I normally go over each section a couple times. Do my whole house. Then start all over and just use water. I always use HOT Water also. Just using water, I still get more dirt out. In the end, the carpets are nice and clean. I make sure I go over them a few times to make sure it sucks up as much water as it can as it'll dry out faster. I think the Scotch Gaurd helps getting the carpet clean once again. So you need to use this stuff before the stains are there so that they are scotch guard protected. Depending on how dirty your carpet is, is what level to set the machine. A hallway, for example, gets a lot of traffic. Heavy use!!! If it's not really that dirty, set it to normal. Then you don't go through the cleaner so fast.
Some people maybe should look at not wearing shoes in the house!!! I don't know what you're doing to get your carpet so nasty, but this stuff is not a miracle worker. You have to care a little bit about where you live. Clean far more often. Maybe use one of the small machines to clean right away just so the carpet doesn't look like a disaster zone. Looking not as bad as before is not good. If should look NEW when done. If you take care of your carpet, it will last a very long time.