24 August 2005
MAKING THE MOST OUT OF USED WATER
If you use an average top-loading washing machine six times a week, itâ€™ll probably send close to 1000 L down the drain in one week alone. Add to that your dishwashing, shower and bath water, and youâ€™re soon up to 4000 L a week for the average family of four.
The wastewater from our kitchens, laundries and bathrooms (not from toilets) is called â€˜grey waterâ€™, or â€˜used waterâ€™ â€” it really isnâ€™t wastewater, as you can still make good use of it in your garden. And if you invest in a properly installed grey water pre-treatment system, you can also use grey water for toilet flushing or in the laundry.
However, there are some environmental and health concerns with grey water, so itâ€™s important you contact the environment protection agency in your state, your health department and local council before you start reusing it.
If you want to reuse manually saved grey water:
Use only the rinse water from your washing machine to water the garden â€” it contains lower concentrations of detergents.
Water different areas in your garden to avoid chemical build-up in one particular area.
Avoid detergents with sodium perborate â€” it's a bleaching agent and a source of boron, which may reach toxic levels if it accumulates in one spot.
For hygiene reasons, use grey water only on plants that wonâ€™t be eaten.
Don't use dirty nappy water.
Don't reuse your wastewater if anyone in your family is unwell or has a contagious virus.
Don't use water from a dishwasher because the detergents can make it quite caustic.
Choose detergents with low or no phosphorus, especially if you live near a water source.
Itâ€™s best not to store grey water and keep adding to it (unless itâ€™s a properly installed system), as bacteria in the water will multiply quickly for the first few days, especially if itâ€™s warm. Theyâ€™ll then stabilise and start to die off, unless you add more grey water.
If you want to install a grey water pre-treatment system, do all of the above, plus:
Consult your sewage removal authority if you intend to redirect all or a major part of your used water.
Consult a licensed plumber for advice on the best system for your needs.
Inform your water supply authority of any changes to your plumbing.