There was a thread in the off topic section that recommended a product called kennel odor eliminator for getting cat pee off an antique rug. My cats were having litter box wars in the basement over Christmas and despite trying every product I could find including Anti Icky poo, Urine Gone, Nature's Miracle Cat Urine Eliminator etc. I ripped about a 12 foot section of carpet up to throw away. Hubby was throwing a fit because it would mean re-carpeting the entire basement so I told him once it warmed up I would try one more time to clean it. I took it outside and worked on it for over three hours. I hung it over the railing outside for over a week while we had a dry spell and it got better but not perfect.
The cat odor eliminator came and I put it in a sprayer like you would use for weed killer and sprayed the carpet liberally on both sides. That stuff is miraculous! Not even a trace of an odor! I will never be without a bottle of this stuff ever again! Thanks so much for the recommendation!
Sorry, I thought I posted that I bought the cat version. It does have a strong scent, sort of minty/herbal but it goes away relatively quickly. I put a cap full in my carpet cleaner with the cleaning solution and cleaned all the carpets in the whole house! The scent faded quickly and was gone by the time the carpets were dry. I put some in a spray bottle and am actually misting the litter boxes after I clean them out. I LOVE this stuff! Should have bought the gallon size.