 : Andy crawls through 500 yards of an 18" sewage pipe to escape the  prison. The ancient sewer pipe would have been filled with methane  gas, carbon dioxide and ammonia fumes and too little oxygen to  support the exertions of the escapee in the time required to crawl  the distance. He should have passed out and suffocated shortly after  beginning his escape. Additionally, when he first breaks the pipe it  shoots up like water pipe under pressure. Once inside, the water is  not moving. And when he gets to the stream that this supposed sewer  pipe drains into, the water is pristine.