In the middle of a severe drought a few year back, Australians were encouraged to recycle water for use on the garden. This ‘grey’ water was explained as a valuable resource which would normally be flushed down the drain. It is true that this water is a wasted resource and can be used again, but with care. There are a few things you need to know before you use it on your lawns or garden.

  1.  Firstly you need to be aware of what was added to this water. Was it for washing your hands and having a bath, or was it used for washing clothing in a washing machine?
  • If natural soap was used such as a bar or liquid made from animal or vegetable fats, then this is biodegradable and safe to use on all areas.
  • However if it contained chemical detergents as found in washing powders and liquid ‘soaps’, this may not be as safe. You will need to check on the packet to see that the product is totally biodegradable. The Material Safety Data sheets will have more information on how the ingredients will affect the environment. (I will be showing you soon on how to access and read these MSD sheets).

However – there is still a major problem on top of the chemicals this water may contain.

2.  You should also know how salty your soil is. If you live near the sea you will be getting salt deposited in your soil every day. Certain soils are naturally salty and there is an increasing problem of soil salinity in countries like Australia.

Grey water can be very high in salt and flooding the same area in your garden can build up salts to toxic levels. If your soil is already slightly saline then you are in danger of making it too salty for plants to grow well. Growth can be restricted and flowering and fruiting affected. The soil biota also does not escape its effects. Micro-organisms, fungi and earthworms can be greatly reduced and these are the things that improve soil quality and breakdown nutrients for plants to use for growth.

If you live in a climate with good rainfall then the salts may be leached out and you won’t have as much of a problem. However, keep in mind the run-off to streams and rivers, and the water table.  But in dry or drought affected areas the salts tend to build up and can permanently damage your soil.

My advice would be to :

  1. Only use water containing natural soaps or biodegradable detergents.
  2. Do not apply it to food crops, only to the ornamental garden beds and lawns.
  3. Move it about the garden so it does not become concentrated in one spot.
  4. Only use it when water or rainfall is scarce.

The best way to use grey-water is to treat it first. This is usually done by running it through reedbeds and into a sump. I will be producing an article on how to do this soon on my website, Keep a look out for it!