- Home
- Site Analysis
- Site Use
- Passive Design
- Water
- Minimising water use
- Stormwater controls
- Rainwater Systems
- On-site Wastewater Treatment
- Septic Tanks: Overview
- Septic Tanks: Design Checklist
- Aerated Wastewater Treatment Systems
- Disposal Systems
- Care and Maintenance
- Greywater: Uses and Safety
- Greywater: System Design and Installation
- Greywater: Gravity and Pumped Systems
- Greywater: Filtering and Treatment
- Greywater: Irrigation Systems
- Composting Toilet Systems
- Material Use
- Energy
- Health and Safety
- Other Resources
Water
Designing homes to use water efficiently, reduce costs and cope with more frequent droughts or storms.
Greywater: Gravity and Pumped Systems
Greywater used for irrigation can be sent to the surge tank and/or outfall using gravity or a pumped system. Whichever system is chosen, it should be designed so that the tanks holding the water empty fully rather than letting the greywater sit for extended periods of time.
Gravity diversion systems
Gravity diversion systems take greywater from the laundry and/or bathroom into a surge tank and, from the tank, into the irrigation system. They are only possible when there is sufficient fall from the laundry/bathroom drain to the surge tank and from the surge tank to the irrigation system.
The surge tank can be any type of suitable container that holds the initial surge of water but does not store it. The surge tank should be vented, have an overflow which is trapped and discharges directly into the sewer or on-site outfall, and be sealed and vermin proof.
- Diversion of water from washing machine or tub for gravity fed irrigation
A three-way valve manually diverts water from the normal drainage system to the surge tank. The machine discharge pipe must not be more than 300 mm above the top of the machine to avoid overloading the pump, and it must discharge into a 40 mm open pipe to avoid the possibility of water being siphoned from the machine.
- Diversion of laundry and bathroom greywater for pumped irrigation
This can only be done if there is sufficient distance between the floor level and the outside ground level to allow a gravity feed to the surge tank. It entails a valve on the appropriate waste pipes to divert the wastewater to the surge tank. The pipes may be individual or combined wastes from the laundry and bathroom (but not from the kitchen). Water is then pumped to the irrigated area.
Pumped diversion systems
Where there is insufficient fall, water can be pumped from the surge tank to the irrigation system using a simple submersible pump and float switch. If necessary, the surge tank may be partially or wholly below ground level.
- Cut away schematic diagram of manufactured gully with pumped diversion to irrigation
Greywater can be pumped from the surge tank to the irrigation system. If necessary, the surge tank may be partially or wholly below ground level.
Commercially manufactured units usually comprise a plastic gully and grating, submersible pump, and an override switch which diverts all the greywater to the sewer or on-site treatment if necessary.
Water unsuitable for irrigation such as kitchen wastewater, discharges to the sewer or on-site treatment plant.
Commercially manufactured units available in New Zealand usually comprise:
- a plastic gully with a grating
- a submersible pump which automatically pumps the greywater to the irrigation system
- either a manual or remote electrically-operated override switch which diverts all the greywater to the sewer if necessary
- a partially self-cleaning filter.
For your clients
To help your clients understand onsite wastewater treatment options, safety issues, and the importance of maintenance, refer them to www.smarterhomes.org.nz/water/on-site-sewage-systems and www.smarterhomes.org.nz/water/re-using-greywater.