The inlet baffle also prevents the floating scum layer from floating back and clogging the inlet pipe. The outlet baffle prevents scum from leaving the tank. If the scum layer reaches the outlet pipe, the pipe will become plugged. Scum in the drainfield will clog soil pores and destroy its ability to treat wastewater. Filtering devices can be installed at the outlet of new or existing tanks to prevent solids from reaching the drainfield.
Regular maintenance is required to keep the filters from clogging and causing backups.
Clogs in the inlet or outlet pipes can be unplugged through the inspection pipes. Inspection pipes must always be capped. The manhole is often buried below ground level. It may be raised from the cover of the tank with concrete or plastic rings for easier access. There may be more than one manhole, in which case they are usually located at the ends of the tank.