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- 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: Irrigation Systems
Always check with the local authority to ascertain what restrictions may apply such as:
- minimum distance of discharge from boundaries, waterways, wells and bores, and the sea
- maximum allowed daily discharge rate.
Greywater which has not been disinfected will contain bacteria. Health risks from greywater used for irrigation can be minimised by:
- ensuring that it does not pond on the surface
- not spraying it – this can create aerosol droplets that can drift in the air; all discharge should be below the surface
- not using it for vegetables – it is suitable for shrubs, flowers and fruit trees
- siting the children’s play equipment or play area away from the irrigated area.
Greywater may contain chemicals from cleaning products, detergents and bleaches that can contaminate the soil and kill plants. The quality of the greywater can be improved by avoiding:
- harsh detergents, softeners and whiteners
- bleach or cleaners with chlorine
- cleaners containing boron.
Greywater from laundries may have higher concentrations of chlorine and harsh chemicals.
Greywater tends to be strongly alkaline so should not be distributed around plants that prefer acidic conditions.
Distribution of greywater
The solids in greywater tend to block small holes in perforated pipes or small diameter drip lines. This tendency can be reduced by filtering but then the filters will tend to clog and will need regular cleaning or replacement.
Distribution options are shown below.
- Subsoil gravity-fed irrigation trench
These are filled with large aggregate metal and rely on absorption and/or transpiration, or in areas of good soil permeability, mulch.
- Mulch-filled swale irrigation
Mulch-filled swales are channels filled with pine bark mulch. Water is discharged through small diameter slotted pipes. The mulch prevents physical contact with the water.
- Proprietary greywater irrigation system
There are several manufactured systems available, typically using a pump to distribute water.
Whichever distribution system is used it should incorporate a distribution box and a branched drain network so that water can be diverted to ‘rest’ each area in turn.
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.