How do you stop a one year old rescued pit bull from peeing inside?

If he is pottying in the house I definitely would limit his freedom! Even though he's older and mostly trained he's in a new environment. Using a crate will teach him how to hold it while inside the house. Sometimes dogs need a refresher course of sorts. Make sure you are cleaning the spots up with an enzymatic cleaner to actually break down the smell so he doesn't think he's allowed to pee there like he would outside. If you don't have a "go potty" command I would start using one so he knows what is expected of him as soon as he goes outside once he goes then he can play or do whatever. Also, make sure you are keeping his feeding and potty times on a very strict schedule while doing all this. It helps you better estimate when he needs to go. I hope that helps!

Consider the fact that he is a rescue and you can't be sure of his history. Maybe there was some negativity with regard to going to the bathroom and he simply cannot help it. One of my dogs tinkles every time he's afraid and/or over excited. My suggestion would be that each time he goes outside, give a little love time before you bring him in. And if he doesn't go once he's in, give a little more. If he does go inside, no love time. Practically ignore him for a few minutes. He'll eventually get the connection. Make a real fuss, "good job!", etc... But not too much... too much excitement may ruin your efforts.