BioSeptic AWTS: An Owner’s Guide to the Performa and S-TEN NR

BioSeptic is a NSW company that makes concrete aerated wastewater treatment systems (AWTS), and it has two domestic models on the current NSW Health register: the two-tank Performa and the single-tank S-TEN NR. Both are rated for a household of up to 10 people, both need a service every three months, and both are built from concrete rather than poly.

This guide covers how your system works, what the certificate says you must do, what the warranty covers and the faults that set the alarm off, with a checklist near the end for buyers.

We’ve kept this to what BioSeptic and NSW Health publish. Where something isn’t published, we say so rather than guess. For the wider brand field, see our AWTS brands comparison.

BioSeptic and its two registered models

BioSeptic Pty Ltd is based at Smeaton Grange, in Sydney’s south-west. Its own history says it was incorporated in 1992, began developing its AWTS at the University of Western Sydney, and started trading in 1993 after gaining NSW Health accreditation. It makes its tanks at its Western Sydney facility, and the founding family has since created Sydney Water Tanks and Conforce, a supplier to the precast concrete industry.

BioSeptic describes its AWTS range as 100% concrete construction, and its S-TEN NR brochure says the tank is cast in one piece from fibre-reinforced 40 MPa concrete.

As at the register update of 22 September 2026, NSW Health lists two BioSeptic domestic systems:

A naming quirk: the register calls the two-tank model the “Performa 2000 Advanced”, while the certificate itself, issued 5 November 2025, names it the “BioSeptic Performa 2020 Advanced AWTS”. Both carry certificate number STS-AWTS047, so they are the same accreditation.

BioSeptic’s S3500 technical sheet also lists S2500, S3500 and S5000 systems, for larger dwellings and commercial premises. If you have one of those on a house block, ask your council what approval is on file for it, because the register’s two BioSeptic entries are the domestic models above.

How the Performa and S-TEN NR work

The two designs run the same treatment train. The difference is how many tanks it’s spread across.

The two-tank Performa. The Performa is the older design; BioSeptic’s S-TEN NR brochure says it has been in continuous production since 1993.

Wastewater from the house runs into the first tank, a partitioned septic tank. Heavy solids sink, fats and oils float to form a crust, and anaerobic bacteria begin breaking down the organic load. Settled liquid then flows into the second vessel, where it passes through two aeration chambers in a row. A blower pushes air through diffusers near the base of those chambers, and bacterial support media give the aerobic bacteria a large surface to live on.

From aeration the water moves into a still clarifier, where remaining solids settle. An airlift returns that settled sludge to the septic tank, which also helps with nitrogen reduction, and a second airlift skims any floating material back to the first aeration chamber. The clear water then flows through an erosion chlorinator into the pump well. According to the certificate, the chlorinated water is held for three pump cycles before it’s pumped out to your irrigation area.

The single-tank S-TEN NR. The S-TEN NR does the same job inside one tank. BioSeptic says it condensed the Performa’s process into a single one-piece concrete tank with six separate chambers: two septic chambers, two aeration chambers, a clarifier and a pump chamber. Because the tank is poured in one piece, the manufacturer’s point is that there are no joints between chambers to leak.

The process is the same sequence: settle, aerate, clarify, chlorinate, pump. The certificate lists a total design capacity of 7,027 litres and around 2,311 litres of emergency storage between the normal water level and the top of the chamber walls, which is the buffer that fills if the pump stops.

The “NR” stands for nutrient reduction. During accreditation testing, the certificate records total nitrogen falling from an average of 69.4 mg/L to 52.78 mg/L (about 24 per cent) and total phosphorus from 10.98 mg/L to 9.20 mg/L (about 16 per cent). BioSeptic’s brochure says the nutrient reduction rating lets it be installed in sensitive areas that call for a higher level of treatment. Your council decides if a site needs an NR model, through your wastewater report and Section 68 application.

What the certificate says about servicing

The Performa’s certificate is issued under the Local Government (General) Regulation 2021 (the S-TEN NR’s, issued in April 2022, cites the earlier 2005 Regulation), and your council applies the conditions to your approval to operate. Both certificates carry the same maintenance conditions. The owner must:

• hold a service contract or agreement of at least 12 months with a service agent
• have the system serviced every three months once it’s installed and commissioned
• use a service agent who is employed or authorised by the manufacturer, uses parts that meet the accredited specification, and sends a NSW Health “Local Council Service Report” to council after every service
• not service the system themselves unless they’re an authorised agent

Each quarterly service must at least check the chlorinator and top up disinfectant, the pump and blower, the alarm, slime growth on the media, the sludge return and the irrigation area, and include on-site tests for free residual chlorine, pH and dissolved oxygen. BioSeptic’s owner’s guide lists the same items and adds an annual look at sludge build-up in the septic chamber.

On the council side, Cessnock, for example, requires quarterly servicing by a suitably qualified service technician and asks for the report within seven days of the service, with electronic lodgement as its preferred method. Other Hunter councils run their own lodgement channels, so check yours.

BioSeptic services its own systems and says it provides three-monthly servicing across NSW. Its owner’s guide also allows for a local agent or another provider authorised by your council. BioSeptic is one of the brands listed on our AWTS servicing page, where our quarterly service runs $90 to $150 a visit. Because the certificate ties servicing to the manufacturer’s authorisation, ask any provider, us included, to confirm that authorisation for your model before you sign a 12-month agreement.

First-year servicing and the warranty

BioSeptic’s website says the first year of servicing is included when you buy a new BioSeptic system. The S-TEN NR owner’s guide puts it as four complimentary services, starting from the date you move in, with the first about three months after occupancy. That’s why the guide asks new owners to return a Notice of Occupancy: it’s how the service department knows when to start the clock and whether there’s a dog or a locked gate to plan around.

The warranty needs a careful read because BioSeptic’s documents don’t all say the same thing.

• The website headline is a “30-year concrete warranty”, and one product page adds that terms and conditions apply.
• The S3500 technical sheet lists a 30-year warranty on concrete components and a two-year conditional warranty on pumps and blowers.
• The S-TEN NR owner’s guide gives a one-year parts-and-labour warranty on mechanical and electrical components, extended to two years with a BioSeptic service agreement. It lists extra warranties that apply while BioSeptic services the system: up to 15 years on the concrete tank and structural parts, up to 5 years on internal pipework, and up to 2 years on the standard irrigation system, irrigation pump and air blower.
• The guide says the warranty is conditional on a continuous service agreement with BioSeptic, and excludes things like flooding, lightning, subsidence and incorrect installation.

If a warranty claim matters to you, get the terms that applied to your specific unit in writing from BioSeptic. Don’t rely on the headline figure alone.

Both certificates separately set an expected service life of 5 years for mechanical and electrical parts and 15 years for other components. That isn’t a warranty, but it’s a fair guide to when a blower or pump is due for replacement.

Common BioSeptic alarm faults and what they mean

BioSeptic’s alarm panel uses three lights, and the owner’s guide spells out what each one points to.

• Green light off. No power. Check the circuit breaker; if it won’t reset, call an electrician. BioSeptic notes it can’t do licensed electrical work, and neither do we.
• Yellow light (low air). The air tube may have come off, the blower may have stopped, or a pipe inside the tank may be broken.
• Red light (high water). The water level is too high. If the power has only just come back on, the tank may simply be overfull and the pump will bring it down. Otherwise the pump may have failed or the irrigation line may be blocked or disconnected.

To silence the buzzer, hold the mute button for two seconds. A quick tap won’t do it. The alarm sounds again after 24 hours if the fault is still there. The guide says not to turn the power off unless the service department tells you to, and to cut back on water use (baths, washing, dishwasher) until the fault is fixed. It also notes the alarm is designed to come on early, so there’s no need to panic.

Low chlorine is the other common finding at a service. The service manual lists causes such as tablets wicking up and not dropping, a canister not seated properly, or a late service. For more on the chlorine side, see how often AWTS chlorine tablets need topping up, and for alarms across all brands, why your AWTS alarm is beeping.

If the fix turns out to be a part, our prices are $650 to $1,400 for an air blower replacement, $600 to $1,200 for a submersible irrigation pump, and $120 to $250 for a blower diaphragm service kit. Anything electrical at the power point is an electrician’s job.

Desludging a BioSeptic

Quarterly servicing doesn’t empty the septic chamber. BioSeptic’s service manual has the technician measure sludge at the fourth and eighth service; if sludge and scum have reached the transfer holes in the baffle, the owner is told to have the tank pumped out. In practice, most AWTS need a desludge every 3 to 5 years on top of quarterly servicing. Our full AWTS desludge and pump-out is $450 to $750.

On a two-tank Performa, the pump-out focuses on the first tank, where the solids collect. On the S-TEN NR, the septic chambers are inside the one tank. BioSeptic publishes a sheet on how to unlock and lift its septic tank lids, which is on its downloads page. Leave the aeration side to the service agent.

Buying a property with a BioSeptic system

A BioSeptic on the block isn’t a problem in itself. A neglected one can be. Before you commit, work through these checks, or have them done in a pre-purchase septic inspection ($250 to $500, with a written report).

1. Identify the model. Both certificates require each unit to be permanently marked by the manufacturer. Look for the model plate on the tank or the details on the alarm panel, then match it against the NSW Health register.
2. Check the certificate dates. The S-TEN NR certificate runs to 31 December 2027 and the Performa to 31 December 2030. If a certificate has lapsed by the time you buy, ask council how that affects the approval on file.
3. Ask for the service history. Every quarterly report goes to council. Ask the seller for recent reports, or ask the council what it has on file. Gaps are a red flag.
4. Ask council about the approval to operate. Ask whether it needs to be reissued in your name and what conditions are on it.
5. Test the alarm and look at the irrigation area. Ponding, run-off, bare soil or a sour smell around the spray area all point to trouble.
6. Ask when it was last desludged. If nobody knows, budget for a pump-out soon after you move in.
7. Ask BioSeptic about the warranty. Its warranty is tied to a continuous service agreement, so ask whether anything is left and whether it passes to a new owner.

Our guide to buying a property with a septic tank in NSW covers the conveyancing side in more detail.

What about BioSeptic prices?

BioSeptic doesn’t list system prices on its product pages; it asks you to enquire, and it offers a site assessment, help with the wastewater report and council application, and installation by its own team or your builder or plumber. For a supply price on a new BioSeptic, go to BioSeptic directly.

For context, our range for a complete new AWTS installation is $15,000 to $25,000 or more. That work is carried out by licensed plumbing and drainage contractors we work with; their NSW licence number appears on every quote. Once it’s in, budget for quarterly servicing ($90 to $150 a visit, or $360 to $600 a year) and a desludge every few years.

If your BioSeptic alarm is going, or you need a service or a pump-out in the Hunter, call 0468 278 123.

Frequently Asked Questions

What BioSeptic models are approved in NSW?

As at the NSW Health register update of 22 September 2026, two BioSeptic domestic systems are listed: the two-tank Performa Advanced (certificate STS-AWTS047, expiring 31 December 2030) and the single-tank S-TEN NR Advanced (STS-AWTS057, expiring 31 December 2027). Both are rated for up to 10 persons. Check the register before a new install, because certificates are time-limited.

How often does a BioSeptic need servicing?

Every three months. The NSW Health certificate makes quarterly servicing a condition, along with a service agreement of at least 12 months with an agent employed or authorised by the manufacturer. A report goes to your council after every service.

Is the first year of BioSeptic servicing free?

BioSeptic says the first year of servicing is included with a new system. Its S-TEN NR owner’s guide describes this as four complimentary quarterly services starting from the date of occupancy, which is why it asks new owners to return a Notice of Occupancy form.

What does the yellow light on a BioSeptic alarm mean?

It signals low air pressure. BioSeptic’s owner’s guide says the air tube may be disconnected, the blower may not be working, or a pipe inside the tank may be broken. Hold the mute button for two seconds, keep the power on, reduce water use and call your service agent.

Does the BioSeptic 30-year warranty cover everything?

No. The 30-year figure refers to the concrete, and BioSeptic notes terms and conditions apply. Its S-TEN NR owner’s guide gives much shorter warranties on mechanical and electrical parts and makes the extended warranties conditional on a continuous BioSeptic service agreement, so get the terms for your unit in writing.

How often does a BioSeptic need pumping out?

Most AWTS need a desludge every 3 to 5 years in addition to quarterly servicing. BioSeptic’s service manual has the technician measure sludge in the septic chamber at the fourth and eighth service and recommend a pump-out once sludge and scum reach the baffle’s transfer holes.

Sources and further reading

• NSW Health, Aerated wastewater treatment systems register: BioSeptic model names, certificate numbers, person ratings and expiry dates, current as at 22 September 2026.
• NSW Health certificate STS-AWTS047, BioSeptic Performa 2020 Advanced: two-vessel design and chamber capacities, blower specification, servicing conditions, 12-month agreement, service life, effluent standards.
• NSW Health certificate STS-AWTS057, BioSeptic S-TEN NR Advanced: single-vessel design and capacities, emergency storage, blower specification, nitrogen and phosphorus test results.
• BioSeptic, home page: 30-year concrete warranty, first year of servicing included, quarterly service scope.
• BioSeptic, About: company history, University of Western Sydney development, 1993 accreditation, Smeaton Grange base.
• BioSeptic, AWTS product range: treatment stages, concrete construction, AS/NZS 1546.3 compliance statement.
• BioSeptic, S-TEN NR product page: model description and links to its certificate and manuals.
• BioSeptic, S-TEN NR brochure (PDF): six chambers, one-piece fibre-reinforced concrete tank, Performa in production since 1993, nutrient reduction.
• BioSeptic, S-TEN NR Owner’s Guide (PDF): complimentary services, warranty terms and conditions, alarm lights, mute behaviour, troubleshooting, service agent options.
• BioSeptic, S-TEN NR Service Manual (PDF): quarterly service programme, sludge measurement at the fourth and eighth service, low-chlorine causes.
• BioSeptic, S3500 technical data sheet (PDF): warranty terms on concrete components, pumps and blowers; BioSeptic model line-up by capacity.
• BioSeptic, How it works: Western Sydney manufacture, site assessment and council application support, installation options, three-monthly servicing across NSW.
• BioSeptic, Household sewage treatment: 30-year warranty on concrete tanks, terms and conditions apply.
• BioSeptic, Servicing: three-monthly servicing requirement and what BioSeptic’s service includes.
• BioSeptic, Downloads: owner’s guides, manuals and the lid unlocking instruction sheet.
• Cessnock City Council, Quarterly AWTS service reports: quarterly servicing by a suitably qualified technician and the seven-day reporting window.