Roots are a common culprit in broken and blocked sewer lines. A root as small as a strand of hair can penetrate a clay sewer pipe and within a few years completely choke off the flow. As the roots grow, they can ultimately crack the clay pipe causing further damage, even resulting in surface sinkholes. Snakes and blades wont help when the roots get this bad. 
  Pay attention to where your sewer line leaves your house when planting shrubs or trees. If you have slow draining pipes, this may be the cause.

Grease is another common problem we run into when repairing sewer lines. Something as harmless as pouring leftover oil from your frying pan into the sink WILL block your pipes. What starts out as a liquid becomes an extremely hard material that will not let anything by. Do yourself a favor and let the oil harden in the pan, then throw it in the trash