Just because your new dog is old enough that he should know where to potty doesn’t mean that he actually does. An adult dog has the necessary muscle control to hold it for longer periods of time, but if no one ever taught him the potty training rules then he’s the equivalent of a brand new puppy. Age should not be equated with housetraining prowess, so it’s a good idea to treat any dog new to your home as if he’s still learning the potty training ropes.
One of the easiest ways to prevent accidents is learning to recognize when your puppy needs to go out. Most puppies will sniff the ground when they’re getting ready to potty, but there are many other more signals that happen prior to sniffing. Puppies that pace, seem distracted and walk away from play are subtly signaling that they have to go out. If your puppy tries to sneak out of the room, take a potty break right away.
It’s best not to punish the puppy for making a mistake. Instead, focus on praising appropriate bathroom behavior. If you catch your puppy in the act, interrupt it by saying “No!” in a firm voice or clapping your hands loudly, then take the puppy outside to finish going to the bathroom. Never swat your puppy, yell at it, or try to rub its nose in the mess.