Hello - I need help! My 9 yr old male Miniature Pincher has been potty trained for the full 9yrs. He has never urinated in my house until now. He has been neutered for 8 yrs. We recently had to dog sit for a relative, the dog was also 9yrs old, potty trained and neutered and he stayed with us for 1 week. Once that dog left, my male started peeing on everything!! The fridge, garbage can, bed, hamper, bathroom tub, you name it, he peed on it. We have cleaned our house top to bottom w/bleach and natures miracle items and he continues to pee. He doesn't do it in our presence. If we leave the kitchen open or bathroom door open, he will go and pee in there if we are not paying attention. I took him to the vet and he was fine, no bladder infection or anything the vet could see. This has now been going on for about 6 months. We are about to move in to our first house and I am terrified he will start peeing all over the new home. What is going on here? Please help!

He probably notice the other dog and that the other dog was roaming free so he decide to mark his territory so next time he won't have to worry

It sounds like he's re-marking his territory. You might want to invest in a crate and re-train him.