What is greywater and how can I use it?

Greywater is typically water from baths, showers, hand basins and washing machines. It does not include water from the toilet, kitchen sink or dishwasher. Greywater replaces the need to use mains water for watering gardens or lawns and can potentially save thousands of litres of drinking water each year.

Just what is greywater? Greywater is wastewater you can collect from your shower, bath, washing machine rinse cycle, hand basins and laundry tub. Greywater does contain micro-organisms, chemical and physical contaminants - such as nutrients, dirt, lint and sand - so you must keep this in mind and it use it sparingly in the garden to avoid salt or nutrient overload.

Benefits of greywater

Reusing greywater provides a number of benefits - as well as reducing the amount of drinking water you use. It can help to reduce the amount of treated water discharged to the environment, it can help to irrigate your garden during dry periods and can help to reduce your water bills. However there are disadvantages to using greywater as there is a potential for pollution and undesirable health effects if the greywater is not reused correctly. There is also the initial cost of a greywater system and plumbing requirements to consider.

Greywater systems

If you wish to use untreated greywater (straight from your showers, baths and washing machines) in your garden, you can chose to either use a bucket or install a sub-surface irrigation system. Untreated water can only be irrigated using a sub-surface system, where the irrigation is buried at least 10cm below the surface of soil or mulch.

There are systems that can be purchased that can be connected to plumbing in your home to allow for the treatment of greywater and for its reuse in flushing toilets, washing machines and surface irrigation. Greywater systems vary greatly in price, depending on the complexity of the system and the intended end-use for the water. A simple diverter can cost under $100, while complete treatment systems can cost several thousand dollars.

Do I need approval?

Customers are advised to contact MidCoast Council to determine what approvals they may need for greywater diversion devices. For greywater diversion devices, any installations connected permanently to the house drainage are required to be inspected by MidCoast Water Services, who has the responsibility of ensuring the installation of greywater devices meet the appropriate plumbing standards.

How to use greywater properly

Do:

  • maintain your system to ensure it is working correctly
  • use low phosphorus detergents
  • diverted greywater (untreated) should only be used on the garden and not always in the same spot
  • apply diverted greywater to the garden by a below ground seepage pipe. This will reduce human exposure to the water
  • Use greywater only during prolonged warm, dry periods: use only what you need to meet the plant's water requirements
  • ensure greywater is diverted to the sewer during wet periods
  • Install a diversion system that is 'fail-safe', where the greywater will automatically be diverted to the sewer if the greywater system blocks or malfunctions
  • Stop using greywater if you smell odours and your plants do not appear to be healthy
  • wash your hands after watering with greywater and after gardening in greywater irrigated areas
  • use less fertiliser when irrigating with greywater
  • ensure greywater does not contaminate any source of drinking water: extreme care must be taken to ensure there is no cross-connection between the greywater re-use system and the drinking water supply

Don't:

  • never water vegetable gardens if the crop is to be eaten raw
  • never use greywater that has faecal contamination, for example: wastewater used to wash nappies
  • never store untreated greywater for more than 24 hours
  • never drink greywater or allow children or pets to drink or play with greywater
  • never allow greywater to flow beyond your property boundary or enter stormwater systems
  • do not use kitchen wastewater (including dishwashers) - it contains highly concentrated food wastes and chemicals that are not readily broken down by soil organisms
  • do not allow greywater to pool or stagnate as this will attract insects and rodents, which may transmit disease
  • never top up a rainwater tank or swimming pool with greywater