A wad of paper towels flushed down a toilet can clog the pipes and create a backup of waste into the building. The best way to avoid this is to not flush paper towels down the toilet. But let's assume that it is too late and the pipe is clogged with paper towels. Many times the clog can be quickly removed using a simple drain snake.
Locate a sewer line clean out. The best place to start is outside. If you can not find one outside then look in the basement or crawlspace.
Remove the clean out cap which is usually threaded into the pipe. It may be cast iron or PVC plastic.
Feed the drain snake into the clean-out with a push and pull action. Progressively push the snake through the sewer line until you feel resistance.
Move the snake back and forth against the place of resistance. Continue until the snake freely advances past the resistance point.
Retract the snake by pulling it out of the pipe clean-out.
Replace the clean-out cap.
Run water from the highest point in the building and observe the clean-out to make sure there are no leaks.