Tree roots invading drains are one of the most common drainage headaches for New Zealand homeowners, especially in older properties where clay or concrete pipes run beneath mature trees. You can tackle minor root intrusions yourself using chemical treatments or hired mechanical tools, but serious blockages or damaged pipes will need a licensed drainlayer. Here's what you need to know before you start.
Understanding the Problem First
Tree roots are drawn to the warmth and moisture inside drain pipes. They typically enter through joint gaps, cracks, or deteriorating seals — common in older clay or concrete pipes. Once inside, roots grow quickly and can cause slow drains, gurgling sounds, or complete blockages. Before attempting any DIY fix, it helps to know how bad the intrusion is. If you have persistent or recurring blockages, a CCTV drain inspection (available from many drain cleaning companies) will show you exactly what you're dealing with.
DIY Method 1: Chemical Root Killers
For early-stage or minor root growth, chemical root killers are the most accessible DIY option. These products typically contain copper sulphate or dichlobenil and work by killing root tissue on contact.
How to use them:
- Purchase a root-killing product from a hardware store such as Bunnings or Mitre 10. Look for products specifically labelled for drain or sewer root control.
- Follow the manufacturer's instructions carefully — dosage and application method vary between products.
- Flush the product down the affected drain (usually a toilet or cleanout point closest to the blockage).
- Allow the recommended dwell time, which can be several hours to overnight.
- Flush thoroughly with water afterwards.
Important: Chemical treatments kill roots but do not remove them. Dead root material breaks down slowly and may still cause partial blockages for some time. These treatments work best as a preventative measure or for very early intrusions.
Safety note: Copper sulphate and similar chemicals are toxic. Wear gloves and eye protection, keep away from children and pets, and never mix with other chemicals. Check the product label for disposal guidance and be aware that high concentrations can harm septic tank bacteria if you're on a septic system.
DIY Method 2: Mechanical Root Cutting (Drain Snake / Auger)
For more established root growth that is causing a blockage, a mechanical drain snake or electric auger with a root-cutting head can physically cut through roots and restore flow.
What you'll need:
- A drain auger or electric eel — these can be hired from most tool hire shops around NZ (check your local Mitre 10 Hire or Bunnings Tool Hire).
- Protective gloves, old clothing, and eye protection — this is a messy job.
- A bucket and hose for cleanup.
Steps:
- Locate your drain cleanout access point — usually a capped pipe at ground level near the house or along the drain line. If you can't find one, you may need a professional to install one.
- Remove the cleanout cap carefully (have a bucket ready in case of backflow).
- Feed the auger cable into the pipe and advance it slowly until you feel resistance from the roots.
- Engage the cutting head and work it back and forth to cut through the roots.
- Withdraw the cable slowly, clearing root material as you go.
- Flush the drain with a garden hose to clear debris.
- Repeat if needed.
This method clears the immediate blockage but, like chemical treatment, does not fix the underlying cause (cracked or poorly jointed pipes).
Preventing Roots from Coming Back
- Combine methods: After mechanical clearing, follow up with a chemical root inhibitor to slow regrowth.
- Regular maintenance: An annual chemical treatment can help keep roots at bay in problem areas.
- Consider the tree: If a particular tree is repeatedly causing issues, you may need to weigh up removal or root barriers — consult an arborist.
- Pipe relining: If roots keep returning, it may be worth investigating pipe relining (a no-dig repair method), which a licensed drainlayer can carry out. This seals cracks and joints from the inside, removing the entry points roots exploit.
What You Can and Cannot Do as a Homeowner
In New Zealand, drainlaying is restricted work under the Plumbers, Gasfitters, and Drainlayers Act 2006. This means any work that involves connecting to, disconnecting from, or repairing the drain itself (including pipe replacement or relining) must be carried out by a licensed drainlayer. You can read more about licensing requirements at the Plumbers Gasfitters & Drainlayers Board.
As a homeowner, you are generally permitted to:
- Use chemical treatments poured down existing drains.
- Use a hired mechanical auger to clear a blockage through an existing cleanout point.
You are not permitted to dig up and replace pipes, alter drain connections, or carry out repairs to the drain structure without a licensed drainlayer.
For work that may require a building consent, always check with your local council first. MBIE Building Performance has useful guidance on what work requires consent.
When to Call a Professional
Call a licensed drainlayer or drain cleaning specialist if:
- The blockage is complete and DIY methods haven't worked.
- You notice sewage backing up into the house — this is a health hazard.
- A CCTV inspection reveals cracked, collapsed, or badly offset pipes.
- Roots keep returning despite repeated treatment.
- You're unsure where your drain lines run.
- The problem is on the public side of your boundary — contact your local council or Watercare (Auckland) as this may be their responsibility.
A qualified local drainlayer can diagnose the problem accurately and carry out any restricted work legally and safely. You can find licensed drain cleaners and drainlayers in your area at tradedirectory.co.nz.
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