|I visited this site about a month ago, along with about 50 other sites, as well as spoke to my vet. I am happy to state that I have conquered the cat pee issue on both levels. Level one of course being the cats actually peeing and Level two, the smell. Here is what I did:
Brief history: We had to put our wonderful Great Dane to sleep about 3 weeks ago, which we believe upset the cat mojo. I steam cleaned the carpet and pulled up a horrible cat/dog pee smell. I called and had a prof carpet cleaner come out and deep heat steam the carpet BAD IDEA! WORST IDEA EVER!!!! The heat and the badass steamer pulled up (what I later found out) all the old pee from the previous tenant. $130 later, the house smelled worse. I then realized that my girls (the cats) were nailing little pees all over the area of the carpet, day in and day out. Every morning for two weeks I would wake up and there would be new fresh puddles. The obvious answer seemed two fold and inhumane: one, leave them outside all the time, but I live in a rural area with coyotes and mt. lions so that didn't seem fair, two, euthanize them so they wouldn't get dragged off by something bigger than them. I decided to call the vet.
Vet said "lock them in the bathroom with a litter box, food and water and nothing else for 5 days - you have to re-boot their brains to using the cat box" I did it. It was horrible, the guilt, the reluctance, the self-doubt... but I stood firm. I would spend time with them in there, use the litter scooper and move litter around while chanting "good girls using their litter box!" Sunday morning, I took the younger of the two and walked her out to the back deck where I had placed a litter box. I shut the door and left her out there, moments later I looked out the window and lo and behold, she was peeing in the litter box, not the lawn. The older of the two, who is nervous of constitution and hates the outdoors, was placed in her litterbox periodically and told that she was a good girl and then given a treat when she came out. Over and over this happened for two days. I gather the girls at night and put them in the bathroom with a treat and food and water and let them sleep in there and let them out in the morning. It sounds mean, but do remember, they cant be trusted if you are not watching them, so to save the carpet, it is necessary, and really much more humane then the above alternatives. Anyway, it worked. They both use the littebox again. Also, tinfoil the area off where they pee, they hate it and it keeps them out.
Level 2: The smell.
Don't steam clean. Deal with the smell, then if you have to clean your carpet, do a chem dry where it wont bother the pad. If the cats stop peeing, the smell will eventually go away to where you cant smell it. I honestly don't think there is a product on the market that gets the smell totally out to where the cats cant smell it, so really you have to fix the behavior and keep them away from where they pee.
What I did: Gallons and Gallons of Natures Miracle. Locate the spots however you can, black light, or like me, just smell every square inch of the room and nail every spot. I mean SOAK IT!! Sometimes, this will bring up a nasty brown stain from the pad. Don't worry, this is a three part process. Let the soaking dry all the way...or at least until it is dry to the touch. Get a spray bottle and another gallon or two of Natures Miracle and just spray and spray and spray every area on top. This is to get the smell out of the actual fibers of the carpet, which we all seem to forget about since we are preoccupied with "getting it down to the pad". Spray and spray some more. Let it dry and spray again. This will get rid of the stains as well that you pulled up when you did the soak. One important thing to remember about NM, if its worse its a sign that it is nearly over. Always when you treat these spots they smell worse when wet, but NM really works and if you keep treating it and keep the cats AWAY from the spot so they don't keep nailing it, you can deal with the smell. And the woman who posted earlier was right, it can take weeks for it to dry so be patient and keep misting the spots.
So, in short: Lock the cats in an UN-CARPETED AREA for 5 days with food and water and lots of love time with you, sit on the floor of your bathroom and tell them what good girls/boys they are, make them sleep in there at night EVERY NIGHT! stay strong, you can do this and they get used to it and do not care at all, put a box outside if your cat is inside/outside before you let them out of their confinement and carry them outside and put them in the box, do not feed them during the day out there, you need them to be hungry enough that they want to come in and eat STILL IN THE BATHROOM, and then shut them in, don't steam clean, tinfoil off the area, NM to soak stains, then NM to spray the fibers. Give them lots of loving and treats when they use the box.