A septic tank riser is the large pipe that comes straight up from the septic tank that allows the tank to be easily accessed for cleaning and maintenance purposes.  The riser extends slightly above ground level as to not be obtrusive or is sometimes flush with ground level.  

Septic tank baffles are the component within the septic system that keeps the solids in the septic tank.  It is important to make sure the baffles are maintained.  They can decompose from exposure to the gases in the tank over time and cause major problems in your septic system.

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