Greywater treatment and reuse: what's allowed, what it costs
Written by Septic Help editors Last reviewed
Greywater is everything that drains from showers, baths, basins and the laundry — not the toilet (that's blackwater) and, in most rulebooks, not the kitchen sink either, because grease and food scraps make kitchen water closer to blackwater. Reused well, greywater keeps gardens alive through water restrictions and takes real load off a septic system. Reused badly, it's a health hazard and a neighbour dispute. The rules sit with your state and council, but they follow one consistent logic everywhere: the less you store and treat it, the simpler the rules; the more you want to do with it, the more approval you need.
The three rungs: bucket, divert, treat
Bucketing — carrying laundry or shower water straight onto the garden — is allowed in every state without approval, and it's the only greywater method that is. Diversion uses plumbing to send untreated greywater directly to garden irrigation, with no storage. Treatment runs greywater through an accredited treatment unit, producing water clean enough for wider uses like subsurface irrigation of larger areas and, with the highest treatment classes, toilet flushing and washing-machine supply. Each rung up adds cost and approval requirements.
Greywater diversion devices
A greywater diversion device (GDD) is a valve-and-filter arrangement that a licensed plumber tees into your waste pipes, with a switch so you can send water to the garden in dry weather and back to the septic or sewer when it rains or when you're washing nappies. Queensland's official guidance is typical: devices must be WaterMark-approved, installed by a licensed plumber, fitted with a diverter switch, and irrigation should be subsurface or low-level — and you must "check approval requirements with the local council before installing a greywater diversion device". Untreated greywater must never be stored more than 24 hours; it goes septic quickly.
Expect to pay roughly $300–$1,500 for the device plus plumbing, or up to about $3,000 with a pumped subsurface irrigation network. Gravity "laundry-to-landscape" arrangements sit at the cheap end.
Greywater treatment systems
A greywater treatment system (GTS) is a small accredited treatment plant — filtration, biological treatment and disinfection — that produces water to a standard your state certifies for reuse. They make sense for large gardens, houses on tank water wanting to flush toilets with recycled water, or unsewered blocks where the council wants greywater handled to a higher standard. Installed costs run roughly $6,000–$16,000 depending on capacity and irrigation, and like an AWTS they come with servicing obligations and a power bill. On an unsewered block, greywater can also simply go to the existing septic — reuse is an option, not an obligation.
State rules at a high level
- QLD: greywater use is regulated under the Plumbing and Drainage Act; council approval requirements apply to diversion devices and treatment plants (treatment plants need pre-approval). Bucketing and a washing-machine hose to the garden are fine without approval.
- NSW: in sewered homes, a compliant GDD generally doesn't need council approval if it meets the NSW greywater reuse guidelines; a treatment system needs approval under s68 of the Local Government Act. Unsewered properties fold greywater into their on-site sewage management approval.
- VIC: permanent greywater systems are regulated through the EPA's onsite wastewater framework — treatment systems require a council permit; simple diversion for immediate subsurface use is treated more lightly.
- WA: greywater reuse needs local government approval, using Department of Health–approved products under its Code of Practice.
- SA, TAS, NT, ACT: similar pattern — health-department-approved products, council/authority sign-off for plumbed systems, bucketing always allowed.
The exact form names and fees are on our state approval pages, and a licensed plumber in your area will know the local council's appetite — that's a five-minute question in a quote request.
On septic already?
Diverting laundry water can meaningfully extend the life of tired absorption trenches by cutting daily flow — a legitimate, cheap intervention worth discussing before a repair-or-replace decision. But keep the diverter switchable: your septic still needs to take everything in wet weather.
Household rules that apply everywhere
- Never store untreated greywater for more than 24 hours.
- Keep it off vegetables eaten raw; irrigate ornamentals, lawns and fruit trees at ground level.
- Don't let it pool, run onto neighbouring properties or reach stormwater drains.
- Divert to sewer/septic when washing nappies or when anyone in the house has a gut illness.
- Use garden-friendly, low-sodium, low-phosphorus detergents — your soil keeps the score.
- Kitchen wastewater stays out unless it passes through a grease trap or treatment system.
Cost snapshot
Bucket: free. Diversion device installed: $300–$3,000. Treatment system installed: $6,000–$16,000 plus servicing. Compare whole-of-system options in our cost guides.
Common questions
Do I need council approval to reuse greywater?
Bucketing never needs approval. Plumbed diversion devices need a licensed plumber and, depending on your state and whether you're sewered, may need council sign-off. Treatment systems need approval everywhere. When in doubt, one phone call to council settles it.
Can I store greywater in a tank for later?
Not untreated — after about 24 hours it turns septic and smells. Only water from an accredited greywater treatment system can be stored, because it's been disinfected.
Is washing-machine water safe for the garden?
Generally yes, on lawns and ornamentals via subsurface or ground-level watering, if you use garden-safe detergents and rotate where it goes. Divert to sewer when washing nappies or heavily soiled loads.
Can greywater go into my rainwater tank?
No — never cross-connect greywater with drinking or rainwater supplies. Highly treated water from an accredited system can supply toilets and washing machines through separate, marked purple plumbing.
Does a greywater system replace my septic?
No. Toilets and (usually) kitchen water still need a blackwater system — septic, AWTS or sand filter. Greywater reuse reduces the load on that system; it doesn't remove the need for it.