We finally solved our carpet problem. Got rid of the carpet. The mold that was growing under the carpet pad was so bad that i stained the wood planks.

We just had the floors sanded and coated. The black stains would not come out even with dumping Clorox right on them.

If the carpets were not changed when they moved into the new apartment then it is not the fault of the cats. There could be old smells from previous occupants and the cats are trying to mask them with their own smell. This happened to us. Fifi used to dump and pee in the same spots over and over. When we got the carpet up we found growing mold right in those spots.

We were about to get rid of Fifi because she was using the carpet instead of the litter box. It broke our hearts. Those spots were so bad that you could smell the difference even after they had been triple sanded and double bleached. Those smells are now buried under two heavy coats of poly-urathane.

It now looks like we have hundred year old Oak flooring. Actually fixingthe problem the RIGHT way has dramtically increased the value of the house. Thanks, Fifi.