Our 5 year old dacshund lab mix has always had this problem with peeing in the house. This came up when he was about 2 years old and we thought he was house trained. He would pee in the same spot In the corner of The living room on the rug. When he started we didn't notice it. when we finally noticed it it was already going through the hard wood floor. When ever we cleaned it with stain remover the next night he would pee on it again. ( he will only do it at night) Now we got a new puppy that seems to be incharge and he is peeing on it every night. Is this a territorial thing or is he just not potty trained. Would be still pee on it if we get a new rug and floor.