Greywater is a great option for your garden watering because most people have a plentiful supply, it doesn't rely on rainfall or vary much with seasons and it reduces the reliance on our drinking water supply.
All the water that comes out of the tap is top quality drinking water, but not all of the activities that we use water for around the house need drinkable water. Greywater is the wastewater from the shower, bath, hand basins or washing machine and doesn't include water from the kitchen sink or from toilets (known as black water). It is considered to be safe, provided that it is used in the appropriate way. Greywater can contain certain disease-causing microorganisms, fats, oils, detergents, salts and more that are derived from the home and personal cleaning. If you switch to greywater-safe detergents and cleaning products, this should minimise the impact on your wastewater.
Greywater can be used for watering gardens and lawns, as well as other activities that don't require drinkable water, such as toilet flush, industrial use, washing vehicles and hosing driveways. Using greywater can be as simple as bucketing it out by hand into the garden, or as complex as installing an automatic diversion, treatment and irrigation system.
Using greywater on your garden
Like most things, what you get out of greywater depends on what you put in. As you know gardens are living things and the chemicals and bacteria we add to greywater can have short and long effects on your garden and indirectly your health. Fortunately most impacts can be addressed by being careful about what you add to greywater and being careful about how you store, treat and use greywater. Because greywater is associated with health risks, it is usually applied to the garden below ground or at least under mulch.
One of the potential impacts of greywater is increasing salt content. This has a long term impact on the soil structure in your garden and is very difficult to fix later on. Common sense tells us to avoid concentrating greywater in one area of your garden, avoid putting too much on and monitor the health of your plants and the state of the soil where you use greywater.
Having given you the warnings many gardeners have really enjoyed being able to recycle their home water in such a rewarding way. A little seaweed solution added in with greywater can act as a gentle fertilizer. You might also note that the phosphates in most soaps will not be appreciated by your native plants but the lawn usually loves them!