Removing an old septic tank is a satisfying project on paper — hire a digger, pull it out, job done. In reality, septic tank removal in New Zealand involves restricted drainlaying work, local council permits, potential hazardous materials, and some genuine safety risks. You may be able to operate the hired excavator yourself for the digging portion, but there are parts of this job that legally must be handled by a licensed professional.
What the Law Says About Septic Tank Removal
In New Zealand, any work that involves disconnecting, decommissioning, or removing a sewage disposal system — including septic tanks — is classified as drainlaying work under the Plumbers, Gasfitters, and Drainlayers Act 2006. This means it must be carried out or supervised by a Licensed Drainlayer.
You can check licensing requirements and find a licensed professional through the Plumbers, Gasfitters & Drainlayers Board. Doing this work unlicensed can result in fines and may create liability issues if problems arise later — for example, if contaminated soil or groundwater issues are discovered.
Do You Need a Building Consent or Resource Consent?
Almost certainly, yes — but the exact requirements depend on your local council. Decommissioning a septic tank typically requires:
- A building consent or at minimum a certificate of acceptance from your territorial authority
- Possibly a resource consent if your property is near waterways, in a sensitive catchment, or subject to regional plan rules
- Notification to your regional council if the tank has been discharging to land or water
Schedule 1 of the Building Act 2004 lists exemptions from building consent, but septic tank removal is generally not exempt — always confirm with your local council before starting work. MBIE Building Performance has useful guidance on when consents are required.
What You Can (and Can't) Do Yourself
Here's a practical breakdown:
| Task | DIY Allowed? | Notes |
|---|---|---|
| Hire and operate an excavator | Yes (with appropriate licence if required) | Excavator hire companies will advise on operator requirements |
| Expose the tank lid and surrounding soil | Yes | Stop before disturbing inlet/outlet pipes |
| Disconnect inlet/outlet pipes | No — restricted drainlaying work | Must be done by a Licensed Drainlayer |
| Pump out and clean the tank | Typically contracted to a specialist | Tank must be pumped before removal |
| Lift and remove the tank shell | Possible with supervision | Coordinate with your Licensed Drainlayer |
| Fill and compact the void | Generally yes | May need to meet council requirements for fill material |
Getting the Tank Pumped Out First
Before any excavation begins, the septic tank must be pumped out by a licensed liquid waste contractor. A tank can contain toxic hydrogen sulphide gas and harmful pathogens. Never enter or lean over an open septic tank — this is a serious risk to life. WorkSafe NZ has guidance on confined space hazards that apply here.
Once pumped, the contractor will typically clean the interior. Some councils require the tank to be crushed in place or filled with sand or concrete rather than removed whole — check your consent conditions.
Using a Hired Excavator: Practical Tips
If your Licensed Drainlayer and council are happy for you to operate the excavator for the dig, here's how to approach it safely:
- Call Before You Dig — contact Dial Before You Dig (0800 248 344) to locate any underground services near the tank
- Start shallow — expose the tank carefully; old concrete tanks can be brittle and collapse unexpectedly
- Watch for asbestos — some older tanks (pre-1990s) may have asbestos-containing components. If in doubt, stop and get a sample tested before proceeding. WorkSafe NZ has guidance on managing asbestos
- Shore the excavation if it's deeper than 1.5 metres — trench collapse is a leading cause of serious injury on worksites
- Have your Licensed Drainlayer on site when disconnecting any pipes
Disposing of the Old Tank
Disposal options depend on the tank material:
- Concrete tanks — can often be broken up on site and taken to a concrete recycler or landfill (confirm with your council)
- Fibreglass or plastic tanks — check with your local transfer station; some accept them, others don't
- Any tank with residual waste — must go to an approved facility; your pump-out contractor can advise
Connecting to a New System or Mains Sewer
If you're replacing the septic tank with a new wastewater system, or connecting to a newly available mains sewer, all connection work is restricted drainlaying work and must be done by a Licensed Drainlayer. The Plumbers, Gasfitters & Drainlayers Board can help you verify a tradesperson's licence.
When to Call a Professional
You should engage a Licensed Drainlayer before you do anything else — they can manage the consent process, coordinate the pump-out, supervise or carry out the disconnection, and sign off the work. For the excavation itself, if you're not confident operating a digger, hire an experienced earthmoving contractor to work alongside your drainlayer. You'll find qualified local earthmovers and drainlayers on tradedirectory.co.nz.
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