How can you remove obstacles in the return pipes in swimming pool without digging up pipes?

You can go to your local hardware store and get a drain king. It is a black expandable bubble looking object that is size applicable, and it attaches to your water hose and expands, filling the pipe on that end, and creating pressure to blow the object back out the way it came. Make sure you get the same size as the pipe you have. 1-1/2" or 2" for example.