Tree Roots in Drains: Why Dunedin’s Older Homes Are Prone and What to Do About It

If your drains keep blocking and the same fixture is the culprit every time, there is a fair chance tree roots are involved. Root intrusion is one of the most common faults we find with the camera in Dunedin, and it is far more common in older homes than newer ones. This post explains why, how to tell if roots are your problem, and what the sensible fixes are.

Why Dunedin’s older homes are so prone to root intrusion

Many Dunedin suburbs are full of villas and bungalows that are close to a century old, and a good number still run on their original drains. Those lines were typically earthenware pipe laid in short lengths, with a joint every metre or so. Over the decades the ground moves, the joints open up slightly, and each one becomes a small gap that lets moisture out into the surrounding soil.

To a tree, a leaking drain joint is the best water source on the section. Roots grow towards the moisture, find the gap, and push in. Once inside the pipe they have water and nutrients on tap, so they thicken and branch until they fill the bore. Established gardens with mature trees, hedges and shelter belts, which are exactly what Dunedin’s older sections tend to have, make it worse.

Newer PVC drains are not immune, but they are laid in longer lengths with solvent-welded or rubber-ring joints, so there are fewer places for roots to get in. That is why the problem shows up so much more often in pre-1970s properties.

Signs that roots are blocking your drain

• The same drain blocks again and again, often every few months, even after it has been cleared.
• Blockages get gradually worse rather than appearing suddenly.
• Slow drainage or gurgling from several fixtures at once, which points to the main line rather than a single trap.
• A patch of lawn or garden that stays greener or wetter than the rest, sometimes directly over the pipe.
• A mature tree or hedge sitting close to the route the drain takes to the street.

None of these prove roots on their own, which is why we always recommend looking rather than guessing. A CCTV drain inspection lets us see exactly what is in the pipe and where it is, and it tells us whether the pipe itself is still sound or has cracked around the intrusion.

Clearing the roots

For a first blockage, or where the pipe is otherwise in good condition, we cut the roots out with high-pressure water jetting. The water blasting head slices through the root mass and flushes the debris out of the line, restoring the full bore of the pipe rather than just poking a hole through the blockage. We follow up with the camera to confirm the line is clear.

Be realistic about what this achieves. Cutting roots is like pruning: the tree is still there and the gap in the joint is still there, so the roots will come back. How quickly depends on the tree species, the season and how badly the joint has opened up. For some properties an annual clear is a perfectly sensible way to manage it. For others it becomes a treadmill of callouts, and that is the point at which a permanent fix makes more financial sense.

Fixing the problem for good

The permanent solution is to remove the entry point. In practice that means replacing the affected section of drain with new PVC, laid with sealed joints so there is nothing for the roots to find. Where the camera shows the whole run is in poor condition, replacing the full length is often better value than patching it joint by joint.

That work is a combination of excavation to expose the line and drainlaying to install and connect the new pipe. Because we do both in-house, the job is planned as one piece of work, the hole is only open once, and we backfill and reinstate the area when we are done. On a typical residential job the affected section can be replaced in a day.

If a tree is the root of the problem and it sits right on top of the line, it is worth having an honest conversation about whether it stays. Sometimes a drain can be re-routed around a tree you want to keep. Sometimes the tree has to go. The camera footage makes that decision easier because it shows exactly where the roots are coming in.

A note on root killers and DIY fixes

Chemical root killers poured down the drain can knock back fine roots for a while, but they do nothing about the gap the roots came through, and some products are hard on older pipes and on the environment. A hired drain snake will often punch a hole through the root mass and get water moving, which feels like a fix until it blocks again a few weeks later. Neither approach tells you what condition the pipe is in, which is the piece of information that actually decides what you should do next.

Roots in your drains? Start with a look

If you are dealing with a drain in Dunedin or wider Otago that keeps blocking, a CCTV inspection is the quickest way to find out whether roots are the cause and how far the damage goes. From there we can clear the line, quote a permanent repair, or both. Call Drain Clearing Otago on 027 474 2274, day or night, or send us a message to arrange an inspection.