Septic Tank from Bunnings: Can You Buy One and Put It In Yourself in NSW?

You can buy a septic tank from a hardware or rural supply store in NSW, Bunnings included, but you can’t legally drop it in the ground and connect it yourself. The model has to hold a current NSW Health certificate of accreditation, your council has to approve the installation under Section 68 of the Local Government Act 1993 before any work starts, and the drain from the house to the tank is licensed draining work.

So buying the tank is the easy part. The tank is also only one piece of a septic system, and the shelf listing won’t show you the rest: the site and soil assessment, the disposal area, the pipework and the council inspections.

This guide covers what to check before you buy, what an off-the-shelf tank does and doesn’t come with, and the situations where buying the tank yourself actually makes sense.

What you’ll find when you search for a septic tank at Bunnings

Search Bunnings online for “septic tank” and you’ll see septic treatments and pump wells alongside poly septic tanks listed under the tank maker’s name (Polymaster’s 3,100 and 4,550 litre tanks have been listed there). What’s listed changes, so read the individual listing for the maker, model and capacity. Those details are what matter for everything that follows.

Tank makers also sell well beyond hardware chains. Polymaster, for example, says its septic tanks are available through more than 1,600 agricultural and plumbing stores across Victoria, South Australia, New South Wales and south-east Queensland. The approval rules are the same whichever store you buy from.

A note on price. We don’t quote retail tank prices here because they change and they vary by store. The shelf price is for the vessel only. The rest of this article explains why that number tells you little about what the finished job costs.

Check the tank is on the NSW Health register

Section 40 of the Local Government (General) Regulation 2021 applies to models of septic tanks, collection wells and other sewage management facilities that are “generally available for purchase by retail”. Section 41 then says a council must not approve installing one unless it is built to a design covered by a NSW Health certificate of accreditation that is in force. A tank from a store shelf is exactly what those sections are aimed at. If the model isn’t accredited, council can’t approve it, however good the tank is.

To get that certificate, NSW Health’s vessel accreditation guideline requires the maker to hold third-party certification to AS/NZS 1546.1 (the guideline cites the 2008 edition), the Australian Standard for septic tanks. The tank has to be marked under that standard and carry the certifying body’s product certification symbol. The guideline also requires any septic tank over 2,050 litres to have a baffle wall splitting it into two chambers.

How to check a tank before you pay:

1. Get the maker’s name, the model and the capacity in litres from the listing or the tank label.
2. Open the NSW Health septic tanks and collection wells register.
3. Find the maker, confirm that exact capacity is listed, and read the certificate expiry date on that line.

Read the expiry date closely. When we checked on 28 September 2026, the register still showed some entries with expiry dates that had already passed (31 December 2025). A certificate has to be in force when council approves the installation, not just when the tank was made.

As an example of what a current entry looks like: as at 28 September 2026, Polymaster’s listing covers 3,100 and 4,550 litre septic tanks, collection wells and 700, 1,000 and 1,300 litre pump wells under certificate STCW020, expiring 31 December 2026. That tells you the model is accredited today. It doesn’t tell you the tank suits your block.

Size is set by NSW rules, not the shelf label

The capacity tables in AS/NZS 1546.1 (Appendix C) and AS/NZS 1547 (Appendix J) don’t apply in NSW. NSW Health’s guideline sets its own formula: a fixed sludge allowance of 1,550 litres plus 150 litres per person per day for all household wastewater, with a minimum of five persons and a maximum of ten in the calculation. That works out to at least 2,300 litres for an all-waste tank, and more as the person count rises, which NSW Health bases on the number and size of bedrooms.

Your council and the site assessment may push the size higher again. Our septic tank size calculator gives a rough figure for your house, and the approved design gives the final one. Buying a tank before you know that number is an easy way to end up owning one you can’t use.

Council approval comes before the hole

Section 68 of the Local Government Act 1993 lists “install, construct or alter a waste treatment device or a human waste storage facility or a drain connected to any such device or facility” as an activity that needs council approval first. Operating the system needs a separate approval.

The application isn’t a one-page form. Section 26 of the Regulation says it must include a scaled plan, full specifications of the system, and a site assessment covering climate, geology, hydrogeology, topography, soil composition and vegetation for the effluent area. Muswellbrook Shire Council’s guide adds evidence of NSW Health accreditation, sizing and disposal calculations, and servicing arrangements to its list.

Then there’s the step that catches people who went ahead early. Section 34 of the Regulation makes it a condition of every installation approval that the system isn’t used until council has told you in writing that it was installed substantially in line with the approval. Cessnock City Council says it cannot grant retrospective approval for installation or alteration work already done; at best, depending on the circumstances, it may be regularised through an approval to operate.

What that means on the ground:

• Don’t dig, set a tank or connect anything until you hold the Section 68 approval.
• Leave work open for council’s inspections. Each council books them differently.
• Keep the approval, the inspection sign-off and the plumber’s paperwork together for when you sell.

Each Hunter council’s lodgement channel, fees and inspection steps are laid out on our septic system replacement page, so we won’t repeat them here.

Who is allowed to put it in

NSW Government guidance defines draining work as the construction, alteration, repair and similar work on a sanitary drain, and says this “includes work on a house drain connected to an onsite wastewater management system”. Doing that work without a licence is a breach of the Home Building Act 1989. The maximum penalty for an individual doing unlicensed specialist work, which includes plumbing and draining, is 200 penalty units (section 12), currently $22,000, and the NSW Government page gives the same figure.

The maker will usually say the same thing. Polymaster’s installation guidance states that all inlet and outlet connections must be made by a licensed plumber, and that installation by an unlicensed person voids the warranty and may breach council approval conditions.

On our jobs, installation, excavation, tank setting, trench construction and pipework are carried out by licensed plumbing and drainage contractors we work with; their NSW licence number appears on every quote. What we do is the rest around it: site assessment, system sizing, Section 68 paperwork support, coordination of the job, the final pump-out of an old tank, and pump-outs once the new one is running.

If you’d like to do some of the labour yourself, such as clearing the site, ask your council and the licensed contractor before you start. Don’t assume any part of the drainage or tank work is DIY.

What an off-the-shelf tank includes, and what it doesn’t

NSW Health’s guideline is blunt about this: a certificate of accreditation covers the tank, not the plumbing to or from it, the land application system or the final disposal method. Those are for council to assess. A shelf tank is one component.

Two parts of that list deserve more attention on Hunter blocks.

The disposal area. The tank settles solids. The trench, bed or irrigation area is what actually gets rid of the liquid, and it is sized from your soil. Hunter soils run from heavy clay to river-flat loam to coastal sand, and each drains very differently. No shelf product can size that for you. If you want to understand how a trench works before you talk to anyone, read how an absorption trench works.

Groundwater. A light poly tank in wet ground can float if it’s empty. Polymaster’s instructions say to pre-fill the tank with water to the specified level before backfilling to counteract buoyancy. Other makers set their own anchoring requirements. On a high water table, that detail belongs in the design, not in a weekend job. We compare the two tank materials in more detail in concrete vs poly septic tanks.

When buying the tank yourself makes sense

There are cases where sourcing the tank yourself is reasonable, as long as everything above still happens.

A replacement tank under an approval. If an old concrete tank has failed and council has approved a replacement, the approved design will name a capacity and an accredited type. Buying that model from a store and handing it to the licensed contractor can work, provided you confirm with the contractor first that it’s the tank they’re willing to install and warrant.

Parts, not the whole tank. A lot of what people search for at Bunnings is lids and risers, not tanks. Cessnock City Council lists replacing components like for like, repairing cracks and resealing tanks as work that doesn’t need approval. Muswellbrook’s guide gives replacing a broken or cracked lid or fixing an inspection opening as minor repairs that don’t need approval either. Those are examples from two councils, so check yours. And if a lid has cracked, get it made safe quickly; an open or weak lid is a fall hazard. We fit risers on existing tanks for $250 to $450 so the lid sits at ground level for good.

A new house or subdivision. The approved design will specify the tank. Let the design come first and buy to match it.

When it doesn’t make sense: buying a tank to swap in without approval “because it’s the same size”, buying before a soil assessment, or buying a model you haven’t found on the NSW Health register. Muswellbrook says system replacements, including replacing any part of a failed disposal area, need approval. Cessnock treats changes to the treatment system, the disposal location or method, or the connected drainage as alterations that need approval. Where the line falls for a whole-tank swap on your property is a question to put to your council before you buy.

The old tank doesn’t just stay in the ground either. It needs a final pump-out and proper decommissioning, covered in decommissioning a septic tank in NSW.

What the whole job costs

Because the shelf price only covers the vessel, here is what the complete jobs cost in the Hunter. Installation, trench and pipework jobs are carried out by the licensed plumbing and drainage contractors we work with, and every replacement is quoted after a site and soil assessment; riser retrofits on existing tanks are our own work.

Council application and inspection fees are separate and set by each council. The septic replacement cost estimator gives a rough figure for your property in a minute or so.

Before you replace anything, make sure replacement is the answer. A blocked inlet baffle, a crushed outlet pipe or a tank nobody has pumped in a decade can look like a failed system. We diagnose first. If you’re weighing up a new tank, call 0468 278 123 and we’ll look at what’s in the ground now, measure the sludge and tell you honestly whether it’s a repair or a replacement.

Frequently Asked Questions

Does Bunnings sell septic tanks?

Bunnings’ online range has included poly septic tanks listed under the maker’s name, alongside septic treatments and pump wells. Stock changes, so check the current listing for the maker, model and capacity. Whatever the store, the model must be on the NSW Health septic tank register with a certificate in force before a NSW council can approve it.

Can I install my own septic tank in NSW?

No, not the drainage work. NSW Government guidance says draining includes work on a house drain connected to an on-site wastewater system, and doing it unlicensed breaches the Home Building Act 1989. You also need council approval under Section 68 before installation starts, and you can’t use the system until council confirms in writing that it was installed in line with the approval.

How do I check a septic tank is approved in NSW?

Take the maker, model and capacity to the NSW Health septic tanks and collection wells register and find that exact capacity under the maker’s name. Check the certificate expiry date on that line, because a certificate must be in force when council approves the installation. Some entries on the register show dates that have already passed.

Do I need council approval to replace a septic tank like for like?

Usually, yes, though councils word this differently. Muswellbrook says system replacements need approval, while minor repairs such as replacing a cracked lid do not. Cessnock allows like-for-like component replacement and tank resealing without approval but treats changes to the treatment system, disposal area or connected drainage as alterations, so ask your council before buying a replacement tank.

What size septic tank do I need in NSW?

NSW Health sets a 1,550 litre sludge allowance plus 150 litres per person per day, with a minimum of five persons in the calculation. That gives at least 2,300 litres for an all-waste tank, with the person count based on bedrooms. Your council and the site assessment may require more, so size from the approved design, not the shelf label.

Does a retail septic tank come with everything I need?

No. NSW Health accreditation covers the tank only, not the plumbing to or from it or the disposal area. You still need a site and soil assessment, a designed trench, bed or irrigation area, pipework by a licensed plumber and drainer, and in many cases a riser, an outlet filter or a pump well.

Sources and further reading

• NSW Health: Septic tanks and collection wells register: register of certificates of accreditation under section 41(1) of the Regulation, including model capacities, certificate numbers and expiry dates (checked 28 September 2026).
• NSW Health: Sewage Management Facility Vessel Accreditation Guideline (February 2016): AS/NZS 1546.1 certification and marking requirements, baffle wall over 2,050 litres, accreditation excluding plumbing and disposal area, outlet filters excluded, NSW capacity formula.
• NSW Health: Single domestic wastewater management: index of NSW Health accreditation guidelines and registers.
• Local Government (General) Regulation 2021: sections 26 (application contents), 34 (no use until council notice), 40 and 41 (retail models must be NSW Health accredited).
• Local Government Act 1993: section 68, Part C items 5 and 6 (approval to install and to operate).
• NSW Government: Plumbing, draining and gasfitting work: definition of draining work including a house drain connected to an onsite system, and penalties for unlicensed work.
• Home Building Act 1989: section 12, unlicensed specialist work, maximum penalty 200 penalty units for an individual.
• Cessnock City Council: Unauthorised installation, alteration or operation of an on-site wastewater system: what counts as an alteration, work that doesn’t need approval, and no retrospective approval.
• Muswellbrook Shire Council: Installing or altering an on-site sewage management system (PDF): minor repairs versus replacements needing approval, and Section 68 application documents.
• Polymaster: Septic tanks: stockist network, optional lid and riser accessory, licensed plumber connections, warranty condition and pre-filling before backfill.