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Wastewater
Q: What is wastewater?
A: Sanitary sewers collect the used water from your home. This is what's referred to as 'grey water' and 'black water'. All the water from your toilet is black water and the water from your bath, shower, sink, basin, washing machine and dishwasher etc is grey water.
If you're connected to the public sewage system, the water will run through your sewage pipes into the public system and from there to the local wastewater treatment plant. Once the water has been treated, it can re-enter our waterways.
Q: I'm building in an area with no public sewage system. What do I need to know?
A: If you're not connected to the public sewage system, you have three main options for collecting and treating your wastewater:
- a traditional septic tank
- an on-site domestic wastewater treatment system
- a managed, 'decentralised' wastewater treatment system.
On-site domestic wastewater treatment plants have been commonplace in New Zealand since the mid Nineties. They use a biological process to treat the waste from your toilets, showers, baths, washing machines, dishwashers and basins.
At the end of the process, you have clean, odourless treated water that can be used to irrigate your section.
They can often be adapted to existing septic tanks, and are particularly suited to sites with poor soakage or high water tables, or sensitive environments where the traditional septic tank doesn't meet the requirements of the Resource Management Act because the effluent discharge is not of sufficient quality.
Aerated wastewater treatment systems break down effluent using a process similar to that at most modern sewage treatment plants in towns and cities. The system can be installed discreetly underground.
Several companies manufacture, distribute and supply wastewater treatment systems in New Zealand, and they often have their own installers. However, you do need to be sure you are buying from a reputable firm and that their product is on your local authority's approved list.
Water New Zealand has two useful booklets on the topic for download:
