Originally Posted by Silverwind
But he pooped in my hallway not half an hour after being out for a walk. He obviously has picked up some bad habits at the pound. What do I do?
It's not necessarily bad habits - dogs don't generalize well. Being housetrained in one place and then in a completely new place don't necessarily transfer over well.
You need to go back to basics, treat him like a puppy - praise for going outside, and not a big deal for going inside - just an interrupt and get him outside. Don't allow as much free roam (keep doors closed, etc) and keep an eye on him at all times until he can be trusted. Also, ensure you're cleaning up the messes with a good enzyme cleaner