Cutting, jetting and chemical treatments keep pipes clear – for a while, but UniSA researchers may have found a smarter way to deal with tree root havoc. Daniel Williamson gets to the root of the problem.

Tree roots in sewer pipes have been the bane of existence for utilities, councils and property owners. Once roots find their way into a crack or joint, they expand in search of water (or your toilet), blocking or damaging entire sections of pipe.

In 2020, SA Water reported more than 30,000 cases of tree root intrusion, accounting for nearly 60% of all sewer failures. The water utility spent about $5 million on repairs and maintenance linked to blocked sewer pipes, and across Australia, similar issues plague many networks, making root intrusion one of the most persistent and costly infrastructure challenges.

“In many older suburbs, particularly where earthenware or ageing PVC pipes are common, root blockages make up a large percentage of service calls,” The Jetters Edge group director, Bill Miller says.

“These blockages can range from minor flow restrictions to complete collapses of sewer lines, requiring full excavation and replacement. In some cases, roots will infiltrate at multiple points and regrow even after mechanical clearing, creating an ongoing maintenance burden for home owners and water authorities alike.”

Current industry responses to root intrusion are largely reactive. Jetting, pipe relining and chemical foams are deployed once a blockage is detected. While these techniques can be effective, they rarely prevent regrowth.

One simple fix is to start planting less intrusive trees in residential areas. While it’s a simple fix moving forward that will vastly reduce the amount spent on maintenance, it doesn’t do much for the problem at hand.

University of South Australia (UniSA) researcher Oliver Yang might have solved the problem for good. He says the common solutions – jetting and chemical root control – are only temporary and the UniSA team may have a new method that can eliminate the issue before it even occurs.

“They are only temporary fixes, because the tree roots will usually grow back. Cutting them or applying chemicals addresses the symptom, not the cause. Chemicals can also raise environmental concerns and the roots return more aggressively,” Oliver says.

Bill agrees: “Jetting is still the fastest and most effective way to clear blockages – but it’s temporary. Roots will usually return unless the source is addressed.

“Relining can be very effective in the long term, especially for straight pipe runs. It seals off joints and cracks where roots enter but the downside is the cost – especially for households – and it’s not always suitable for every situation. Chemical treatments like foaming herbicides can slow regrowth, but there are growing environmental concerns. Most professionals treat chemicals as a supporting measure, not a standalone fix.”

Rather than chasing roots after the damage is done, UniSA’s research advocates for a predictive analytics approach. This idea is to model the risk of intrusion based on environmental, structural and vegetation-related factors.

“We can model risk using variables like pipe age, material, diameter, soil type, tree species and climate conditions. That way, councils and water utilities can identify high-risk areas, guide smarter planting choices, choose more appropriate pipe materials and schedule targeted maintenance before blockages occur,” Oliver says.

Bill sees huge potential for proactive, data-driven solutions: “The UniSA study’s focus on predictive analytics could be a game-changer. If we can identify high-risk areas based on tree species, soil profiles and pipe condition, utilities could shift from reactive jetting to targeted inspections or even preventive relining — saving time, money and disruption for everyone involved.

“For our business, early detection tools like CCTV and ground-penetrating radar are already part of the toolkit, but their use is typically reactive. Widespread adoption of predictive models could help shift the industry into true preventative maintenance.”

The method draws from global literature and existing failure prediction models, but few current tools incorporate environmental or vegetation data. This, researchers argue, is a significant gap given how root behaviour is influenced by soil moisture, compaction and species growth patterns.

Aggressive species like eucalyptus, poplars, willows, jacarandas and desert ash can send roots many metres in search of water. In contrast, species like hackberry, willow myrtle, brush box and kurrajong are far less intrusive, which makes them safer choices for planting near pipelines.

The UniSA research examined how each factor involved influenced the main issue of root intrusion, which is called multiple linear regression.

Oliver admits, however, the results showed limitations: “Our study focused on sewer drains, and all the research was in damaged pipes of 150mm, so it isn’t suitable to be used as a variable. The result still showed that the model can only explain a minimal amount of data. This means the multiple linear regression we use is not ideal for predicting the risk. Other models can do better jobs.”

He also acknowledges that, though the concept has promise, it’s hard to tell whether the preventive measure will eliminate the root cause, as the issue is so complex. The biggest barrier is identifying the real culprit of blocking the pipe efficiently and effectively.

“When someone reports a problem, the utility service usually sends a technician to record the issue. What we don’t know is which tree causes the issue and what species. Most of the time, the technician won’t record that, so there is missing data. That is the biggest challenge,” he says.

For now, Oliver’s team has only tried the multiple linear regression study, but plans to try other modelling. The hope is that with more complete and variable data and better modelling techniques, the predictive approach could shift the industry away from continually battling regrowth with costly reactive methods and toward preventing many blockages before they start.

Though still in its early stages, the research points toward a smarter way of managing root intrusion. It’s one that could save utilities millions and protect infrastructure. But until the preventive method is ready, plumbers and jetter companies can still have the pleasure of answering the calls of local councils and utility companies.