Greywater can wet your garden no matter the weather, but you must use it with care.
With another dry summer predicted, gardeners will soon need all the moisture they can get. Diverting your greywater can seem like a simple solution, but Helen Tuton from Sustainable Gardening Australia warns that it’s not so straightforward. “The long term effects of greywater on soil health aren’t known,” she says.
Greywater is the used water from your shower and bath, bathroom basin and laundry (not the kitchen or toilet). Collection systems range all the way from buckets to the big bucks.
No matter how you catch it, Ms Tuton says one thing is crystal clear. “Greywater and edible plants just don’t mix. A lot of fats, oils and salts come out of greywater and just sit in the soil.”
Chemicals, harmful bacteria and other residues in our recycled water damage the good bacteria and fungi that live in healthy soil. “I always recommend that people turn their greywater off over autumn and winter,” Ms Tuton says. “The soil needs a chance to be flushed out with rainwater.”
There are two kinds of greywater: untreated and treated. You’ll need to hire a licensed plumber either way, because both will require alterations to your sewer pipes.
Brent Papadopoulos from Sustainable Plumbing Solutions says that for public health reasons, untreated greywater isn’t allowed to see the light of day. “It must be transferred out to your garden through sub-surface irrigation. It must not pool anywhere and it must be used within 24 hours.”
An untreated diverter system costs between $700 and $2500. “They need regular checking and filter cleaning by the homeowner, otherwise they get blocked,” Mr Papadopoulos says. “Some systems might need attention twice a week. It just depends on the family: what they put down the drain and how hairy they are.”
Treatment systems are much more expensive – from $5,000 to $12,000 – and they require a permit from your local council. On the plus side, however, they’re eligible for a $500 Federal Government rebate and they produce much more versatile water.
“They harvest the same greywater but then they treat it and clean it up to a class-A standard,” Mr Papadopoulos says. “It can be stored and used in the home to flush toilets, wash clothes and also for above-ground irrigation like the good old-fashioned pop-up sprinklers.”
If you’re planning on gathering greywater, Ms Tuton recommends switching cleaning products, especially in the laundry. It’s important to buy products low in sodium and phosphorous. Washing detergents marked NP are phosphorous free, but for full information on different products, refer to independent testers Lanfax Laboratories.
According to Ms Tuton, there’s another puddle for greywater gardeners to avoid. “We’re finding that people are drowning their plants. They’re killing them with love,” she says. “Just because the water’s there, doesn’t mean you need to use it on the garden.”