Greywater Systems in NSW: What You Can Do on a Septic or AWTS Block

A greywater system takes the water from your shower, bath, basins and washing machine and reuses it on the garden, either by diverting it straight to buried irrigation lines or by treating it first so it can go further. If your Hunter property is on a septic tank or an AWTS, you need council approval for either kind, because the NSW rule that lets homes divert greywater without approval only applies where no sewage management facility is installed on the property.

Most greywater advice online is written for suburban homes connected to the sewer. On an unsewered block, greywater is part of your on-site sewage management, and your council treats it that way.

What counts as greywater

Greywater is household wastewater that hasn’t come from a toilet, but the exact definition depends on which rule you’re reading.

For diversion, the Local Government (General) Regulation 2021 defines greywater as water from washing machines, laundry tubs, showers, hand basins and baths, and excludes water from a kitchen, toilet, urinal or bidet. The NSW Planning Portal’s BASIX guidance explains why: kitchen water may be heavily polluted with food particles, oils and fats, so it can only be included if it’s treated.

The Office of Local Government (OLG) onsite wastewater guidelines use a wider definition that includes kitchens and dishwashers, because a treatment system can be built to handle them.

It’s a bigger share of household water than most people expect. The OLG guidelines set design flow allowances for a house on tank water at 120 litres per person per day, and 80 of those litres are greywater. Blackwater from the toilet is only 40. On reticulated or bore water the figures are 150, 100 and 50. Roughly two thirds of what your septic system handles is greywater, so moving it elsewhere affects the whole system.

Diversion, processing and treatment: the three device types

The OLG guidelines describe three kinds of greywater device, and they sit under different rules.

NSW Health describes two forms of diversion device: a gravity device with a hand-operated valve or tap on a fixture’s waste pipe, and a pump device with a surge tank that copes with sudden flows but doesn’t operate as storage.

A treatment system is a different animal. The OLG guidelines describe systems that collect, store and treat greywater using processes such as settling, aeration, clarification and disinfection, and note that some operate much like an AWTS. Every one must be accredited by NSW Health, and a condition of that accreditation is that the owner enters into an annual service contract with a suitably trained service agent.

Processing devices fall in between. The model approval conditions in the OLG guidelines include installation by a licensed plumber authorised by the manufacturer or supplier, servicing every two years by an authorised service agent, and a connection back to the approved sewage system so greywater can be redirected there when needed.

What NSW allows on sewered and unsewered lots

Section 75A of the Local Government (General) Regulation 2021 says domestic greywater diversion needs the prior approval of council, then gives an exemption that applies only if all three of these are met:

• the work is carried out in accordance with the Plumbing Code of Australia
• a sewage management facility is not installed on the premises
• a list of performance standards is met, covering disease, odour, water contamination, soil and vegetation damage, insects and vermin, human contact with effluent, and amenity for neighbours

The second condition is the one that matters in the Hunter’s rural areas. A septic tank or an AWTS is a sewage management facility. So if you have one, the exemption doesn’t apply to you, and diverting greywater needs council approval under section 68 of the Local Government Act 1993. The OLG guidelines confirm that council regulates all three device types and that any use of them in unsewered areas requires council approval.

Treatment systems need approval everywhere, sewered or not. The Planning Portal states that you need council approval to operate a single household greywater treatment system, and council can only approve one that NSW Health has accredited.

The Planning Portal also flags sites where greywater diversion systems shouldn’t be used: shallow water tables, highly porous soils such as sand beds, and ground showing seeps, soaks or springs. If your block sits on sand with groundwater close to the surface, as some Port Stephens properties do, expect that to come up early with council.

Carrying greywater out in a bucket isn’t “domestic greywater diversion” under the regulation, because the definition excludes manual collection. That doesn’t make it risk-free, as the storage section below explains.

NSW Health accredited greywater treatment systems

NSW Health keeps a public register of accredited greywater treatment systems. When we checked on 28 September 2026 (the page was marked current as at 13 February 2026), it listed four:

• Aqua Clarus M800sx, certificate DGTS012, expiring 31 December 2030
• Rootzone G-700, certificate DGTS 010, expiring 31 December 2029
• Ozzi Kleen GTS10, certificate DGTS 003, expiring 31 December 2030
• UltraGTS from Wastewater Australia, certificate DGTS 011, expiring 17 June 2030

The list changes, so check the register itself before you commit to a model. We don’t publish prices for these units; ask the manufacturer or get a quote.

Each system’s certificate of accreditation sets the treatment level it reaches (the register page doesn’t show it), and the level sets the permitted uses. The OLG guidelines summarise it for single households:

If you already have an AWTS

On an AWTS property, your greywater is probably already being reused. An AWTS takes all the household wastewater, treats and disinfects it, then pumps it out to your irrigation area. The Easy Septic Guide notes that aerated systems can treat greywater to a standard suitable for watering non-food plants. The OLG model conditions are firm on food: no wastewater, effluent or greywater from the system is to be used to grow vegetables or fruit for human consumption.

So before adding a separate greywater unit to an AWTS property, ask what you’d gain. Usually not much, unless you want indoor reuse such as toilet flushing, which needs a Level 1 or 2 treatment system or a processing device, plus council approval. Keeping the AWTS itself in good order through quarterly AWTS servicing is usually the better use of money.

How greywater reuse affects tank and trench sizing

Taking two thirds of the flow away from a septic tank sounds like a way to shrink the trench. The guidelines don’t let you assume it.

The OLG guidelines say any design that includes a greywater device must account for all the wastewater the greywater unit doesn’t handle, and for any greywater that isn’t reused in the house. Treated greywater that can’t be reused must go into a properly sized greywater application area or fit within the capacity of the blackwater area, designed to the same procedures as secondary treated effluent under AS/NZS 1547:2012. Processing devices must be connected back to the main system so flows can be redirected to it when needed.

In practice, the greywater still has to go somewhere in wet weeks or when the unit is down for service. Don’t count on a greywater device letting you downsize the trench; ask council first.

Older rural properties sometimes have a split system: a septic tank for the toilet and a separate greywater tank, often with a small grease trap for the kitchen. The Easy Septic Guide says to check and clean the grease trap every 2 to 4 weeks and to clean the greywater tank at least twice a year. We pump out greywater tanks at the same prices as any other tank, from $350 to $500 for up to 3,000 litres, and you can book a pump-out for one the same way.

If your trench is already struggling, a greywater device isn’t a repair. Read the signs of absorption trench failure and get the trench assessed before adding anything to the system.

Risks: storage, salts and detergents

Storage. NSW Health’s greywater reuse document says stored greywater turns septic, and that thermotolerant coliforms have been found to multiply 10 to 100 times in the first 24 to 48 hours of storage, with significant pathogen levels still present after eight days. Its conclusion is that greywater must not be stored, other than temporarily in a surge tank, unless it has been adequately treated. The Easy Septic Guide gives a practical version for split systems: release greywater within two hours of it entering the tank, or it can go bad and smelly. The same logic applies to buckets and drums.

Salts that treatment doesn’t remove. The same NSW Health document notes that treatment systems are designed mainly to treat organic matter and don’t normally remove salts such as sodium, nitrates and phosphates. Common washing powders use sodium salts as bulking agents, making saline greywater; powders using potassium salts, or liquid concentrates, give better-quality greywater. Some detergents contain boron, which can harm plants and animals at high concentrations.

Your soil. The OLG guidelines list sodium from laundry detergents, soaps and cleaning products as a cause of damage to soil structure, and recommend laundry detergents low in sodium and phosphorus. That matters on heavy clay, which already absorbs water slowly, so the detergent you choose matters as much as the device. See septic safe products in Australia for what to look for on the label.

DIY greywater systems: what a homeowner can do

Most “DIY grey water systems” guides are written for sewered suburbs. On a septic or AWTS block, fitting a diversion device, processing device or treatment system means altering sanitary drainage, which is plumbing and drainage work under NSW law. Diversion devices are certified through a WaterMark licence, and the OLG model conditions call for processing devices to be installed by a licensed plumber authorised by the manufacturer or supplier. None of this is a job for a hose and a hardware store fitting.

What you can control is your habits. Pick low-sodium, low-phosphorus laundry products, fit lint filters and sink strainers, spread washing over the week, and use any bucketed bath water straight away rather than leaving it in a drum.

Where we fit in: we don’t install greywater systems. We can assess your site and existing system, help work out sizing, and support the council Section 68 paperwork. Any installation is carried out by licensed plumbing and drainage contractors we work with; their NSW licence number appears on every quote.

What to ask your council before buying anything

Each Hunter council runs its own on-site sewage management program, and the answers depend on your soil, block size and existing approval. Before you commit, ask:

1. Does my current Approval to Operate need to be varied if I add a greywater device, and what do you need with the application?
2. Is my site suitable at all, given my soil, water table and distance to any creek or dam?
3. Which device types will you consider here: diversion, processing or treatment?
4. If greywater leaves the septic tank, will the existing trench or irrigation area stay as it is, or will you want a separate greywater area?
5. What servicing and reporting will be a condition of approval?

Our guide to council OSSM inspection rules in NSW explains how councils rate and inspect systems.

If you’d like someone to look at your system before you talk to council, call 0468 278 123 or ask for a septic inspection. We call you back within 24 hours during business hours.

Frequently Asked Questions

Do I need council approval for a greywater system in NSW?

If your property has a septic tank, AWTS or any other sewage management facility, yes. The exemption in section 75A of the Local Government (General) Regulation 2021 only covers diversion on premises where no sewage management facility is installed. Greywater treatment systems need council approval to operate on any property, sewered or not.

What is the difference between greywater diversion and greywater treatment?

A diversion device only screens greywater and sends it straight to subsurface garden irrigation, without storing or treating it. A treatment system collects, stores and treats greywater, and depending on its treatment level the water can be used for surface irrigation, toilet flushing or the washing machine. Treatment systems must be accredited by NSW Health; diversion devices are not, but are certified under a WaterMark licence.

Can I put greywater into my septic tank?

In most conventional systems, greywater already goes into the septic tank along with toilet waste, and the system is sized for it. Some older properties have a separate greywater tank instead, which the NSW Easy Septic Guide says to clean at least twice a year.

Will a greywater system let me use a smaller septic trench?

Not automatically. The NSW onsite wastewater guidelines require any design with a greywater device to account for greywater that isn’t reused, either in a separate greywater application area or within the capacity of the main one. Council will look at how the system copes in wet weather or when the device is being serviced.

Can I use greywater on my vegetable garden?

Not from an on-site system. The model approval conditions in the NSW onsite wastewater guidelines say no wastewater, effluent or greywater from the system is to be used to grow vegetables or fruit for human consumption. Keep greywater and effluent on lawns, ornamental beds and non-food trees.

How long can I store greywater?

You shouldn’t store untreated greywater beyond a brief surge. NSW Health reports that bacteria in stored greywater have been found to multiply 10 to 100 times within the first 24 to 48 hours, and the Easy Septic Guide advises releasing greywater within two hours of it entering a holding tank.

Sources and further reading

• NSW Legislation, Local Government (General) Regulation 2021, section 75A: approval for greywater diversion, the exemption conditions and the definitions.
• NSW Office of Local Government, Onsite Wastewater Management Guidelines (April 2025): GDD, GPD and GTS definitions, council’s role, treatment levels (Table 5-3), design flows (Table 6-2), greywater application areas, sodium, and model approval conditions.
• NSW Office of Local Government, The Easy Septic Guide: greywater tanks, grease traps, the two-hour release advice and aerated systems watering non-food plants.
• NSW Health, Greywater Treatment Systems register: accredited systems, certificate numbers and expiry dates (checked 28 September 2026).
• NSW Health, Greywater Diversion Devices: gravity and pump devices, no NSW Health accreditation, WaterMark and WTS 460-2016.
• NSW Health, Onsite single domestic wastewater management: NSW Health’s accreditation role, including greywater treatment systems.
• NSW Health, Greywater Reuse in Sewered Single Domestic Premises (April 2000): bacteria in stored greywater, salts, washing powders and boron.
• NSW Planning Portal, BASIX greywater design principles: kitchen water, unsuitable sites, and council approval of accredited treatment systems.