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Septic Systems: What You Need to Know

How a Septic System Works

A standard septic system has two main parts: 

  • The septic tank: A watertight container that holds household wastewater, allowing solids to settle (sludge), oils to rise (scum), and treated water (supernatant) to flow out. 
  • The land application area: Where treated water—called primary effluent—is dispersed, typically using trenches, beds, or a mound system. 

Inside the tank, natural microorganisms break down waste. The leftover liquid flows to the land application area via slotted pipes or arches, soaking into soil or being drawn up to plant roots. 

All septic systems must follow: 

Design and installation must be done by licensed professionals, based on a proper site and soil evaluation. 

Septic System Maintenance Tips

To keep your system healthy and avoid costly repairs: 

  • Mow around trenches to help evaporation. 
  • Keep vehicles and heavy animals off the tank and trenches. 
  • Never cover tanks or trenches with concrete, pavers or soil. 
  • Divert stormwater away from the system. 
  • Avoid using antibacterial cleaners—they kill the good bugs that help break down waste. 
  • Only flush what the system can handle (no nappies, wipes, or hygiene products). 
  • Clean the outlet filter every 3 months. 
  • Have the tank pumped out by a licensed contractor every 3–5 years. 

Need to check your tank? Lift the inspection opening and use a long stick (like a 20mm dowel) to check the sludge depth. If it’s more than 500mm deep, it’s time for a pump-out. 

Signs of Trouble

  • Ponding or soggy patches in the trenches 
  • Foul smells 
  • Slow drains or gurgling pipes 

If your system is malfunctioning, it could pose a health risk. Owners or occupiers are legally responsible for ensuring the system is in good working order. Contact Council if your system is failing or causing a nuisance. 

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