Wastewater management

Greywater is domestic wastewater that comes from kitchens, bathrooms and laundries.

It does not include wastewater from toilets or urinals.

When managed properly, greywater can be reused on lawns and gardens.

Read below to find out more about recycling greywater from your home.

What's in greywater

Greywater can contain:

• dirt
• food
• grease
• detergents, soaps and chemicals
• salts
• harmful micro-organisms.

If it's not managed correctly, it can be a risk to human health and the environment.

Benefits of using greywater

When used responsibly, greywater can be:

• a source of irrigation water all year round
• a relatively easy and safe source of water to access and use
• a good source of nutrients for plants.

Reusing greywater on your garden

When reusing greywater on your garden, remember the following:

• Don't use kitchen wastewater on your garden – it contains fats, oils and grease which can:
  • reduce the amount of air to plants and
  • harm micro-organisms
• Keep children away from areas where greywater is used until it has soaked into the ground.
• Don't let greywater form puddles or run off onto other properties, watercourses and drains.
• Don't keep watering in one spot - salts and other contaminants will build up.
• Rotate greywater use with mains and rain water - this will help flush salts from the soil.
• Don't overwater your plants.
• If plants are damaged, reduce the amount of water used or try a bigger irrigation area.

How to apply greywater

You can apply greywater to your garden using a:

• bucket or temporary hose
• greywater diversion device.

Bucket or temporary hose

Using a bucket or temporary hose is the easiest way to apply greywater.

Don’t store or keep the water for more than a day. Storage can lead to spills and bad odours.

Avoid doing this when it’s raining or soil is saturated to stop greywater running into neighbouring properties.

Greywater diversion device

If you want to permanently divert greywater to your garden, you can install a greywater diversion device (GDD) on your property.

A GDD diverts greywater to a small holding tank and then to an irrigation system that’s below the soil surface.

These systems should be self-draining so that greywater isn't stored for more than a day.

They also have a valve to make it is easy to divert greywater directly to the sewer when it’s raining or when the soil is saturated.

Rules for your GDD

You don’t need approval to install a GDD, but your device must be:

• installed for a single house only
• installed by a licensed plumber and drainer
• connected to sewerage or septic tank.

When using a GDD, you must not:

• store greywater for long periods
• use kitchen wastewater
• use greywater for spray irrigation - the system must release it below the ground’s surface.

Managing kitchen wastewater

Most systems exclude kitchen wastewater from the waste stream because it’s difficult to treat.

You must divert it to a sewer (or septic tank).

Managing laundry wastewater

Most manufacturers advise against using greywater from the laundry trough when it is polluted with:

• dirty nappies
• soiled clothing
• cleaning chemicals.

Read your system’s manual for further instructions.

Reusing treated greywater indoors

You can only use treated wastewater for indoor use in a single house.

Greywater can be reused for clothes washing and toilet flushing.

You must get a licensed plumber and drainer to carry out the internal plumbing works.

Guidelines for using greywater

Follow these guidelines for using greywater responsibly:

• Don't use greywater if other people in the house are sick.
• Don't use greywater from washing clothes covered in vomit or faeces - this includes nappies.
• Don't keep untreated greywater for more than 24 hours to avoid spillage and bad odours.
• Try not to splash greywater.
• Wash your hands before eating, drinking or smoking.