The following photos are examples of what could happen to your pipes, within your septic system, if you do not following proper maintenance.  It is recommended by most counties to get your system pumped every 2 - 3 years.  Regular pumping can decrease the chance of build up & allows your system to work properly. 

You can see in the photo that due to irregular maintenance, the sludge built up & completely clogged the pipe.  This caused back up into the tank & a failing system!