- Site Analysis
- Site Use
- Passive Design
- Water supply
- Building design considerations
- Sanitary plumbing systems
- Drainage systems
- On-site wastewater treatment
- Stormwater control and landscaping
- Water supply
- Material Use
- Wet Areas
- Health and Safety
- Other Resources
Water use, sustainability, and efficiency by choosing quality systems and materials, and providing environmentally friendly solutions.
Designing an on-site wastewater treatment system
The appropriate wastewater treatment system will depend on the site, the required capacity, and compliance requirements.
On this page:
- site considerations
- system options
- system capacity
Also see design checklist.
Site features that must be considered when designing a wastewater disposal system, include:
- Is the water table high or low?
- Does the land become saturated during periods of high rainfall?
- What area of land is available for the system?
- What is the soils ability to absorb moisture, e.g. is the subsoil clay, sand, loam etc?
Note: The amount of land needed for the disposal field depends on the subsoil.
Local authorities or regional councils may have their own bylaws controlling an installation and resource consent may be required. Contact the local authority before you begin to design a system.
Allow for a daily output of 200 litres per person when designing a system. This will enable it to cope with peak discharge rates or temporary overloads. It must also be able to retain the total flow for at least of 24 hours.
The system should also have enough capacity for 35 years of sludge at the following rates:
- for blackwater and greywater 80 litres per person per year
- for blackwater only (where there is separate greywater system) 50 litres per person per year
- for greywater only 40 litres per person per year.
The sewage system capacity must allow for:
- variations in the quantity of effluent to be disposed of
- the possibility that householders will not manage and maintain the system effectively.
Updated: 05 November 2018