Ask what system is installed, where it discharges, who uses and maintains it, what authorisation applies and when it was last serviced and emptied. A targeted pre-purchase drainage inspection can identify visible defects and unresolved questions that a normal home survey may not answer.
When this guide fits
Clues worth recording
- The seller cannot identify the outlet
- The tank or field lies outside the title boundary
- Several homes share the system
- There is odour, wet ground or a recent pump-out
Ask for facts, plans and rights
Request the system description, layout, discharge point, registration or permit, service and desludging records, installation documents and details of changes. Your conveyancer should examine ownership, access, easements and shared cost obligations.
Consider a specialist inspection
A useful inspection records safe access, tank or plant condition where visible, alarms and electrical equipment, flow, outlet evidence and signs of drainage-field distress. It should state limitations: underground condition cannot be guaranteed from surface observations.
Understand future running needs
Budget for desludging, servicing, electricity for powered plants and eventual repair. Check whether vehicle access for emptying is practical and whether the system capacity suits the intended occupancy.
Resolve issues in the contract
If evidence is missing or an upgrade is needed, obtain advice before exchange. Ask your conveyancer how any investigation, retention, price adjustment or remedial obligation should be documented.
A contractor’s verbal reassurance does not replace your conveyancer’s review of rights, responsibilities and regulator documents.
Questions homeowners ask
What people usually want to know
Will a standard home survey inspect the septic tank?
Usually only at a general visual level and subject to access. A separate drainage or private sewage inspection may be recommended.
Is a shared septic tank a problem?
Not inherently, but ownership, access, capacity, maintenance responsibility and cost sharing need to be clear.
Should the seller empty the tank before inspection?
Ask the inspector. A recently emptied tank can make some operating evidence harder to assess, though safe access and service records remain useful.
Sources & review
Evidence behind this guide
Reviewed 1 September 2026. We use primary guidance where available and label trade-body advice clearly.