The Septic Due Diligence Checklist for Buying Rural NSW Property

Buying rural property in NSW with a septic system means inheriting the system’s entire history, including any maintenance gaps, unapproved modifications or pending council obligations. A septic system in good condition is a non-issue at settlement. One in poor condition can cost $5,000-$25,000+ to remediate after you’ve already committed. This checklist covers every septic question worth raising before you sign a contract, and our septic inspection service can complete a pre-purchase condition report if you want an independent technical opinion before exchange.

The Section 149/10.7 planning certificate check

The Section 10.7 planning certificate (formerly called a Section 149 certificate) is one of the first documents your conveyancer should order from the council. For properties with on-site sewage management systems, this certificate may reference the system’s registration, any outstanding council orders or notices, and whether the property is within a prescribed environmental risk zone that affects what type of system is permitted.

Ask your conveyancer to specifically review the certificate for:

• Any outstanding notices to comply related to the sewage system
• Environmental restrictions (waterway proximity, prescribed buffer zones)
• Whether the property is zoned for a category of use that affects system requirements

The NSW planning certificates (Section 10.7) page provides background on what these certificates contain.

Does the property hold a current approval to operate?

This is the most important single question. Under the NSW Local Government Act 1993, any on-site sewage management system requires both an approval to install and an ongoing approval to operate. The approval to operate is renewed through council inspections on a risk-based cycle.

Ask the vendor or your conveyancer to obtain:

• A copy of the current approval to operate from council records
• The date of the most recent council inspection
• Any conditions attached to the approval (some properties have ongoing monitoring conditions)

An expired or absent approval to operate is a significant red flag. It does not necessarily mean the system is non-functional, but it does mean the new owner will need to engage with council to establish the system’s compliance status from day one. See our Section 68 approval guide for background on how the approval system works in NSW.

The PMHC on-site sewage management pages provide council-specific context for Port Macquarie-Hastings properties.

For guidance on how approvals transfer at settlement, see our septic transfer between owners guide.

What tank type, size and age is under the ground?

System type affects maintenance obligations, servicing costs and suitability for the property’s lot size and environmental setting. Before exchange, establish:

Tank type: Is it a conventional septic tank with absorption trenches, an aerated wastewater treatment system (AWTS), a sand filter system, or something older? Each has different servicing requirements and council obligations. Our NSW septic rules overview explains the compliance obligations per system type. If the block is genuinely steep, also check whether the system relies on gravity to reach its trenches or uses a dosing pump to get effluent there, see our steep block septic guide for what that distinction means for maintenance and power-outage risk.

Tank material and age: Older concrete tanks (pre-1990) may have cracked baffles or deteriorating joints. Polyethylene tanks, common from the 1990s onwards, can float on high water table blocks. Ask the vendor for any as-installed documentation.

Approved capacity: The system should be sized for the number of bedrooms. A two-bedroom unit with a 1,500-litre tank is undersized; a standard four-bedroom home typically requires a minimum 3,000-litre primary tank in NSW. If the property already has a granny flat or tiny home added since the original installation, check specifically whether the approval and the system’s capacity were updated to reflect the combined occupancy, see our guide on tiny homes and granny flats adding load to an old system for what that involves.

If no documentation exists about tank type or size, a licensed plumber can locate and inspect the tank as part of a pre-purchase inspection. Our septic inspection service includes tank access and condition reporting.

When was it last pumped, cleaned and inspected?

Ask the vendor directly and request documentary evidence. Documents to ask for include:

• Invoices from the most recent pump-out (showing date, company and volume removed)
• AWTS quarterly service reports for the past 12 months minimum, if the property has an AWTS
• Council inspection notices and any correspondence with council about system compliance

A conventional septic tank on a typical household load should be pumped every 3-5 years. If the vendor cannot produce a pump-out record from within that window, factor a pump-out into your settlement costs or negotiate it as a vendor obligation. Our septic tank pump-out service can be booked pre-settlement if the vendor agrees.

For AWTS systems: quarterly service reports are a condition of approval to operate in NSW. Missing reports are not just an administrative gap, they are a potential council compliance issue that will transfer to you as the new owner.

Trench age and condition: the expensive half

The absorption trenches are often the most expensive component to replace and the least visible from a pre-purchase walk-around. Trench failure rarely happens suddenly; it accumulates over years of solid overload, root intrusion or saturated soil conditions.

Indicators to look for during a property walk-through:

• Lush green strips in dry weather: Effluent reaching the surface and fertilising grass above the trench line
• Damp or soft ground above the trench line: In dry weather, this indicates surfacing effluent
• Structures, paving or garden beds over the trench area: These can compress aggregate, block oxygen exchange, or damage perforated pipes (and make remediation more expensive)
• Large established trees near the trench lines: Root intrusion risk; see repair vs replace septic trenches for what that can mean in practice

A pre-purchase inspection with a licensed plumber can include a probe test or CCTV drain inspection of the inlet pipe to assess trench loading. It cannot definitively assess every metre of trench without excavation, but it can identify obvious warning signs.

If you cannot find the tank lid or locate the trench lines from the vendor’s documents, a professional locating service can often find them using as-installed records or electronic detection.

Water quality and environmental restrictions

Rural blocks in NSW, particularly in coastal catchments like the Hastings, Camden Haven and Lake Cathie areas, often carry environmental constraints that affect what type of system is permitted and where it can be located. These constraints affect:

• Setbacks from waterways: Buffer distances from permanent watercourses, wetlands, and registered bores affect where a system can be sited or expanded
• Prescribed environmental sensitivity: Some blocks sit in high-risk environmental zones that require secondary treatment (AWTS or sand filter) rather than a conventional septic tank
• Drinking water bores: If the property has a bore for domestic water supply, setbacks from the septic system apply to protect the bore from contamination. If the vendor’s system has been poorly maintained, that risk is worse than the setback distance alone suggests; our guide on nitrate risk from ageing septics for bore water households covers what an overdue or neglected system does to groundwater risk over time

Ask your conveyancer to check the contract and council records for any notations about environmental constraints on the on-site sewage system. The Section 10.7 certificate and the approval to operate conditions are the primary sources.

If the block sits on a floodplain, ask specifically whether the tank has ever floated or shifted, and whether it has a proper anchor slab. A lightweight tank on saturated, flood-prone ground can lift out of the ground if it’s pumped empty at the wrong time, and older systems on low-lying paddocks weren’t always built with this in mind. Our guide to flood-prone paddocks: raising and anchoring septic tanks covers what to check and what a proper anchoring setup looks like.

If the property already runs horses, cattle or other livestock, it’s also worth checking where the absorption area sits relative to the grazing paddocks and whether it’s fenced off. Our septic placement rules for acreage with livestock guide covers the compaction and effluent-exposure risks that come with stock grazing over or near a septic system.

If the property already has, or you’re planning to add, a granny flat or second dwelling, check whether the existing system was ever assessed or approved for that combined occupancy. Our guide on dual occupancy on acreage: when one septic isn’t enough covers the sizing, approval and cost implications of adding a second household onto one block’s wastewater system.

For buyer context on the conveyancing side of septic disclosure, see the septic conveyancing red flags guide.

Pre-purchase checklist summary

Use this list in your due diligence process. Items marked (Conveyancer) should be confirmed through your solicitor or conveyancer. Items marked (Plumber) require a licensed plumber’s inspection.

Rural septic buying checklist FAQs

Can I make the vendor fix the septic system before settlement?

Yes, subject to negotiation. It is common practice to include a condition in the contract requiring the vendor to bring the system into compliance before settlement, or to provide a price reduction to offset the buyer’s remediation cost. Ask your conveyancer how to frame this correctly, as poorly worded conditions can complicate settlement.

The property has no paperwork for the septic at all. Should I walk away?

Not necessarily, but it is a significant due diligence gap. Request that the vendor obtain the approval to operate and pump-out history from council and their service provider. If they cannot, commission a pre-purchase inspection and factor remediation costs into your offer price. An entirely undocumented system is a risk, not always a showstopper.

Does the approval to operate automatically transfer to me at settlement?

The approval to operate follows the land, not the person. As the new owner, you take on the compliance obligations attached to the property from settlement day. However, you should still notify council and update contact records after settlement. See the septic transfer between owners guide for what to lodge after settlement.

How much should I budget for a pre-purchase septic inspection?

A basic septic inspection including tank condition and above-ground assessment typically costs $250-$450. Adding a CCTV drain camera inspection can bring the total to $500-$800 depending on the complexity and accessibility of the system. This is a small cost relative to the risk of buying a property with a system requiring $10,000+ in trench remediation.

The vendor says the tank was pumped recently but can’t provide an invoice. Is that enough?

A verbal claim without documentary evidence is not sufficient for due diligence. Request the name of the operator so you can ask them to confirm the service, or commission your own pre-settlement pump-out as a condition of the sale. An operator will typically provide a written record of the service.

Related reading

• Tiny homes and granny flats: adding load to an old system
• Pre-purchase septic inspection checklist
• Selling a house with a septic tank in NSW
• Section 68 approval for septic systems
• Septic conveyancing red flags
• Septic approval transfer between owners
• Repair vs replace septic trenches
• Septic inspection service