How to care for your septic tank

Rural homes, beach homes, holiday homes & older homes often rely on septic tanks for their sewerage treatment and disposal.  As long as these units are properly maintained and their disposal fields protected they should give many years of trouble free service.  In fact, property owners are required to have their tanks pumped out at least every three years in NZ.

If these tanks are not pumped out on a regular basis, settled solids build up, and leave inadequate space in the tank for proper treatment and retention of incoming material. Odours result and in extreme cases the sludge solids can migrate into the drainage field causing field failure.

Products like addwater Septic Liquifier are available which are designed to turn solids into liquids to ensure no blockages occur between the 3 year cycle.


  1. All waste flows to the septic tank.
  2. Watery waste, called “effluent,” fills most of the tank. Anaerobic bacteria begin breaking down the organic material in the effluent.
  3. A layer of sludge falls to the bottom. Sludge is composed of inorganic solids and the byproducts of bacterial digestion.
  4. A layer of scum floats to the top. Scum is primarily composed of fats, greases and oils. The septic tank acts like a settling pond. Greases and oils float to the top. Heavier solids sink to the bottom.
  5. A filter prevents most solids from entering the outlet pipe.
  6. Effluent flows to the drain field. The drain field provides a large area where bacteria can thrive and treated watercan seep into the ground.
  7. Holes in the drain field pipe allow effluent to seep into surrounding gravel.
  8. Gravel around pipes allows water to flow into soil and oxygen to reach bacteria.
    1. Aerobic bacteria in gravel and soil complete decomposition of the waste.
    2. Clean water seeps down into the groundwater and aquifer.


Signs of a failing septic tank system:

  • Septic tank effluent surfacing on your land
  • Strong or bad odours coming from the septic tank or drains
  • Pollution of nearby ditches or streams with effluent
  • Slow flushing of toilets
  • Gurgling in the drains
  • Ground movement (dips) near the septic tank or soakaway drainfield
  • Toilet overflowing
  • Overflow at washing machine hookup
  • Overflows into shower or bath when the sink empties
  • Drain inspection chambers have standing effluent in them. These should be empty.

How to prevent Septic Tank Failures

  • Have your tank desludged every three years by a certified hazardous waste contractor
  • Keep solids, including food scraps, coffee grounds, tampons, wipes and condoms out of your wastewater
  • Check your cleaners are OK for septic tanks (will be on label). Use biodegradable soaps and cleaners.  Do not use blue flush in the toilets
  • Take showers instead of baths
  • Install water saving devices, practice water conservation.
  • Wait for a full load before using the washing machine, and try to stagger your washing through the week rather than doing it all on the same day.
  • Divert stormwater from your disposal field and tank area
  • Ensure the cleaning lid to your septic tank is easily accessible
  • See filters are cleaned every six months
  • Use a Septic Liquifier to prevent solid matter build up between tank cleans.
  • Take care not to damage dripper lines with lawnmowers, weed eaters etc
  • Do not Park vehicles on any part of your treatment system ordisposal field
  • Don’t put bleachers, disinfectants, chemicals or paint down the drain
  • Never connect rain gutters, water tank overflow  or stormwater to septic tank
  • Try not to grow deep rooting trees near the septic tank or drainage field
  • Don’t let weeds block your dripper lines
  • Ensure children don’t play in the disposal field if at surface level

1 thought on “How to care for your septic tank

  1. You got me when you said that it’s possible that your septic tank must have an issue if there are bad odors coming from your it. I will share this with my sister because her house is being surrounded by foul odors. When I visited her house last night, I know that there must be something wrong with her house. I will help her find a septic tank repair company that can help her.

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