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How a Septic Tank works

Waste flows into your septic tank where it settles and is partially broken down by bacteria. Fats and solids remain in the tank. Liquid, which has separated from heavier particles, flows into the disposal field whenever new raw effluent enters the tank. In the disposal field, the separated liquid continues to be treated by natural processes. The type of disposal field depends on soil type, the slope of the section, vegetation and underlying rock.

Your septic tank is a living ecosystem where bacteria do the work of digesting and treating waste.

The contents of a healthy septic tank form 3 layers:

  • Heavy, solid particles settle at the bottom of the tank forming a layer of sludge.

  • Light materials, including fat and grease, float to the surface forming a layer of scum.

  • Raw effluent containing large amounts of dissolved pollutants including salts and nutrients, nitrogen and phosphorus are sandwiched between the sludge and the scum. Raw effluent contains disease causing pathogens such as viruses, bacteria and worms.

Bacteria break down some organic solids, which helps reduce the build-up of sludge. Scum helps prevent odors escaping and stops air entering the tank.

Active Waste Water Treatment Systems

In active new style wastewater treatment systems, the separated liquid flows into an additional aerated or other treatment chamber before entering the drainage field. Systems are more effective at turning the separated liquid into usable waste water because of the aerobic bacterial activity in this extra step. Consequently you should be able to use waste water from wastewater treatment systems in irrigation drip lines, if desired.

How to maintain a Septic Tank System

Signs of a Problem

You may have a problem with your septic system when:

  • There is a bad odor coming from your septic system;

  • Toilets and plugs drain very slowly;

  • Waste water is pooling on the drainage field;


These problems can be caused by any one or more of the following factors:

  • A sludge build up in the tank caused by infrequent emptying;

  • Non-biodegradable chemicals being put down the drains, killing the useful bacteria required to make your septic tank system work efficiently;

  • Other unsuitable items such as fats and grease are being disposed of into the system, this can clog the gravel in the disposal field;

  • There is damage to the pipes, either by tree roots or by fractures in the pipes;

  • The disposal field is water-logged (either through heavy rainfall or too much water going to the system at once e.g. shower/bath water and washing water).

Septic Tank Maintenance

To maintain and protect your septic tank system, we recommend the following:

  • Clean (empty) your septic tank regularly, at least once every three years;

  • If you have a waste-disposal unit for food scraps, your septic tank should be cleaned out annually, as sludge will build up rapidly;

  • Use only toilet cleaners and other detergents suitable for septic tank systems (i.e. avoid using and disposing of bleaches, whiteners, nappy soakers, stain removers & disinfectants (in large amounts);

  • Do not use disinfectants to clean the toilet bowl, as disinfectants will kill the useful bacteria in the tank;

  • Do not dispose of anything, other than effluent and toilet paper in the toilet (i.e., avoid disposing of baby wipes, cigarette buts, sanitary pads, tampons, disposable nappies, condoms in the toilet);

  • Do not dispose of anything, other than water and system friendly detergents down drains (i.e. avoid disposal of grease, chemicals, pesticides and oils, paints, varnishes & paint thinners, cold water soap powders);

  • Protect the drainage field by avoiding driving vehicles or grazing stock on it and divert storm-water away from the area;

  • Do not allow deep rooting trees or shrubs to grow over drainage pipes or the disposal area.

Call us!

Clogged septic tank. Emptying the septic

Regular Service Scheme

NMWaste offer a Regular Service Scheme that provides our customers with services at pre-arranged intervals to the frequency you choose, removing the hassle of organising each clearance.

Septic tanks need to be emptied out regularly to prevent the significant health and environmental risks that can ensue when the tank overflows or malfunctions.

Join our regular service scheme and benefit from priority attention and peace of mind that your septic tank is being cleared as recommended.

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