I had 5 cats (yes, at the same time). After a few years one of them started spraying or urinating outside the litter box. Used all kinds of odor removers. What actually worked on getting cat to stop doing that: Bought 2 of those metal tea leaf holders (that you use instead of tea bags), saturated cotton balls with lemon juice, put them into the tea balls and left the tea balls in the offending spots. I couldn't believe it worked, but it did. Only 're-juiced' them about once a week for 3 weeks. Miracle!