I have two 9 month old kittens. Girl cat uses the litter trays no problem, boy cat seems to go through phases of peeing on the carpet- always in the same few spots near the front and back doors. Sometimes he does it because girl cat is using the tray when he needs it (we do have two trays and he will use either but it seems he picks which one to use each time and won't change his mind!) Once he did it when I was cleaning they tray he wanted to use. Other times I can't find a reason! I've tried a couple of different enzyme cleaners, a homemade citrus spray, vinegar, bicarb, citrus washing up liquid, citrus disinfectant, biological washing powder, boiling hot water. Once I've cleaned it I can't smell it but he obviously can! I've tried putting foil over the area which deters him for a while but eventually he starts to play with it. I've put puppy pads down but he sees that as an invitation to pee on it. Does anyone have any other tips or ideas please? Or can recommend an enzyme cleaner that they know actually works well?