A stench that won't quit.

History, a corner of the carpet was soiled by a foster I had, and by fangie, before I knew he had cystitis. Not sure how long he had been using it, because I was caring for an my senior cat who was on her way out.

So after she passed, I discovered the problem (around two years ago!!) Took care of Fang, he has not more inappropriate peeing, and no one has soiled that spot since.

Problem, the stench will not go away. Initially I used a carpet cleaner which was a big mistake, it just compounded the smell with more smell and made it feel gummy.
Since then I have used enzyme cleaner, poured baking soda and vacuumed, and used the combo of baking soda and hydrogen peroxide spraying it and pouring it to soak in. The hydrogen combo works for around a few months, seems that the smell leaves, but after a few months, if I rub my hand over the spot and then smell my hand, PPUU!!

Why does this keep coming back? Is there a way to be rid of it forever? How much more spraying and soaking can I do? thanks

If it keeps coming back to the point you can smell it on your hand, I'd be inclined to think it is being RE-soiled. Alternatively, you could try the 2 c peroxide, 2 t baking soda and 2 drops detergent--pour it on until it's soaked (as I know you have been doing) then repeat weekly for a month, allowing it to dry thoroughly between applications. If that doesn't work, and you're SURE there isn't a repeat offender...I have no clue.

If it was peed on a lot, the pad under the carpet probably is utterly ruined and moldy. You should replace the carpet. Carpet should generally be replaced every 5 years anyway, and most people don't. My wife and I ripped up the carpet in our new house, owners before us had had it for about 5 years. No obvious problems on top, but it was VERY obvious where their dog had had accidents.

Carpet cleaners and other solutions only get the top, and the more stuff you throw on it the worse it gets underneath. Carpet's the cheapest floor solution for a reason, after all.

hmmmm, it is wall to wall and in a corner. I might be able to pull up that corner and see what's doing underneath. The carpet is in good shape, I am not inclined to replace it, but if I could lift it, cut off a hunk of padding and check out the floor, might be a solution. thanks for the idea.

Yeah, see what's underneath -- mostly it's staples along the edges and you should be able to stick it back down. Also, if it's only a corner and the stuff you have is still being produced, you can usually buy smaller squares of it and fix just the part that's bad, with a barely imperceptible seam.

Rent a professional steam cleaner or pay someone to clean your carpet. No vacuum will get beyond the very top of the carpet and those little mixed vacuum/shampooers are only moderately successful. Steam clean, pour on vinegar, steam clean again, and then let dry. We had a barn cat that came indoors for breakfast in the morning and main reason she was a barn cat is that she always had a fear of the litterbox (all and any litterboxes). For 3 years she peed behind the tv at least once a week and then because the smell was there 2 litters of kittens peed behind the tv. When the barn cat was gone we pulled away the tv, used my mom's steam cleaner and the vinegar, and the smell is gone. My mom also manages apartments and that's what we do after someone with a dog has rented it but add the vinegar to the steam cleaner since it would take forever to spray and pour vinegar on all the carpet in an entire apartment.