I have a 12 year old male who recently insists in peeing inside. All the time. In the past he would almost always go outside (occasionally he needed to mark his territory inside) but now it is completely driving me insane. He recently went and lived with my grandpa for a few weeks and now that he has come back he is peeing everywhere. He has a doggy door and so he is able to go outside, and sometimes I go outside with him and wait for him to go but then I always find little puddles inside. I have tried to catch him in the act but am never able to. Really need some help on some sort of training methods to get him out of this habit. I have also heard there are some kind of cleaning products that can be used on the floor that stop dogs from going there? Do they work at all?