Water
Designing homes to use water efficiently, reduce costs and cope with more frequent droughts or storms.
On-site wastewater treatment
If a public sewerage system is available, NZ Building Code clause G13 Foul water requires that habitable buildings must be connected to it. If a public sewer connection is not available, habitable buildings must be provided with an on-site wastewater treatment system.
Find out about:
- blackwater and greywater
- treatment systems
- statutory requirements
- designing a wastewater treatment system
- septic tanks
- aerated wastewater treatment systems (AWTS)
- land-application disposal systems
- system maintenance
- dealing with problems
- greywater recycling
- composting toilets.
Blackwater and greywater
Blackwater is wastewater from toilets, dishwashing machines and sinks – because the fats, detergents and cleaning agents used in kitchen wastewater, this is considered blackwater and must be discharged accordingly.
Greywater is waste from baths, showers and hand basins.
Wastewater from clothes washing machines may be considered in either category.
Treatment systems
On-site wastewater treatment systems may treat blackwater and greywater in a single wastewater treatment and disposal system, or in separate treatment and disposal systems so that:
- treated greywater is used for irrigation or flushing toilets
- a composting toilet is used in combination with a greywater treatment system.
Both of these options reduce the amount of effluent to be disposed of by the land application system.
A single on-site wastewater treatment system involves two stages of treatment. The first stage may be:
- a primary treatment system such as a septic tank
- a secondary treatment system such as an aerated wastewater treatment system, or an advanced sewage treatment system.
To complete the treatment process, the second stage involves dispersal of partially treated effluent to a land application disposal area where the effluent is treated by bacteria as it trickles through the soil.
In many areas, a primary treatment system is no longer permitted, as the available dispersal area may be insufficient to treat the effluent (particularly with the increase in lifestyle blocks).