This is a great example of a low spot in a septic pipe, where gravity pulls the waste that drains from the house to the lowest point until enough water pressure builds up behind it to force it past and into the septic tank.

 

Many times, the septic pipes become bent because the contractor who installed the system did not fill the septic tank with some water, allowing it to "float" or extrude from the ground slightly, pulling the attached pipes upward with it.