Grey water is a great way to save money, save water and save your garden during the long, hot summer. The average family can generate as much as 400 litres of grey water a day. However, if you want to use this form of recycled water, there are a few basic things to keep in mind.
Know What Grey Water to Use
Grey water is any water that goes down the drain at your house that isn’t from the toilet. That means water from your bath, shower, hand basins and washing machines. You can also think of water from the kitchen sink and the dishwasher as grey water, but because it’s usually got food scraps in it, water from these sources are referred to as having a high “organic load” – which is another way of saying that it’s in danger of being a source for unhealthy bacterial growth.
Keep the Quality of Water High
Your garden is a living thing. To make sure that it stays that way, it’s important to keep its exposure to certain chemicals and bacteria to a minimum. Grey water usually has a much higher salt content than tap water, plus water with a lot of detergent or soap in it can also be a bit of a shock to your plants. Consider discarding water from your washing machine wash cycle but using the water from the rinse cycle. Another option is using “grey water friendly” detergent and soap.
Know Where to Use Grey Water
Avoid concentrating grey water in just one area of your garden. Don’t put too much on and keep an eye on the health of your plants to make sure you’re not doing any damage to your soil.
Make Sure Your Soil is Right
Soils that are very sandy or have a high clay concentration are not good for using with grey water. High clay concentration can lead to water run off issues. Very sandy soil can lead to excessively deep drainage with grey water entering the water table. The best soil type is a loamy type that retains water well without becoming muddy.
Choose the Right Water for the Right Plants
If you think about the sources of grey water in your house, you’ll realise that there is more than one variety. Some sources are better suited to certain applications. For example, if you’re using detergent with phosphates in it, it’s best not to use that on native plants but your lawn will love it. You must also never use grey water on food plants – especially leaf and root crops.
Know What Regulations Apply
Every region in New Zealand has different rules governing the use of grey water, so check with regional council before deciding on greywater. There are some rules that apply across the whole country. If you are using a greywater diversion device (greywater isn’t treated), the irrigation pipes need to be below the surface (100 mm recommended). Don’t store untreated greywater longer than 24 hours – it will start to smell. If it’s raining, divert your greywater away from the garden. Before purchasing a system, ask about the maintenance needs, particularly around cleaning filters.