Septic Tanks

Septic Tanks

Septic systems treat wastewater from toilets and discharge the effluent through a distribution box to the land application area (septic trenches). The septic tanks can range from 1600L up to 4000L and multiple septic tanks on a single dwelling. For system to work properly it needs to be kept healthy to allow the bacteria to break down and digest the waste. A healthy septic tank should form three layers

  • a layer of fats (scum) which floats to the surface to prevent odours and stop air entering
  • a clear layer (settling zone called effluent)
  • a layer of solids (sludge or bio-solids) which sinks to the bottom.

Waste that is not decomposed by the anaerobic digestion must eventually be removed from the septic tank.  If the septic tank becomes overfull or the baffles inside the septic tank decompose, sludge will discharge directly to the application area. If the sludge discharges into the trenches, it may clog the application area requiring expensive repairs or a system replacement.


Products that kill bacteria or contain, bleach, chlorine. antibacterials, disinfectants should be avoided.

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