Why Do Tree Roots Cause Blocked Drains?

Mar 16, 2022

Blocked drains can be caused by a multitude of issues. The most common cause of blocked main house drains in Queensland is tree roots. Even in metro areas, roots are known to invade plumbing systems undetectable by homeowners and tenants alike. Even if you don’t think a tree is close enough to cause problems, you may be surprised at what goes on beneath the surface.

If you’re experiencing signs of blocked drains or haven’t had a drain check in a while, tree roots may be the culprit of the drain problem you have. Luckily this is a pretty common issue, and one Brisbane Metro Plumbing can help you with it quickly and effectively.

Why Do Roots Clog Drains?

We all know that tree roots provide trees with moisture from the soil. Well, your pipes and plumbing are a goldmine that pumps everything trees and plants need to survive. If they crack into a main pipe, you may have a thousand dollar problem. 

Roots grow towards sewer and water pipes because they sense the water and nutrients that flow inside. All it takes is the smallest movement for the pipe to crack and roots can begin to creep inside and grow until you notice a partial blockage or a complete blockage if it’s left untreated. Depending on the size of the root, they may even brute force their way inside over time. 

The way it works is, plants search for fertile soil with a main root, which digs down through the soil. Then when it finds a good spot to set up, it sprouts a bunch of smaller lateral roots to drink up all the water it can. The more water available, the thicker the roots. 

Root plumbing blockages can create a slew of problems, so read on for signs and prevention methods.

Signs That You Have A Root Blockage 

If you think you have roots in your sewer, don’t try to do a plumber’s job. Searching for a sewer line can be disastrous if the pros do not handle it. 

With that in mind, there are ways you can recognise clogged or blocked lines. Remember, early detection saves money, so if you notice any of the following, it’ll be better to call a professional plumber like Brisbane Metro Plumbing & Gas right away. 

If you notice any of the following, you may have root blockages: 

  • Backed up drains 
  • Slow drainage 
  • Bad smells in bathrooms
  • Gurgling toilets or sinks
  • Sewer overflowing outside when used

Stages Of Root Pipe Blockages 

Luckily a root blockage doesn’t happen overnight. Each stage has different signs that help you nip the issue in the bud early on. 

  1. Tree roots tend to enter drains that have cracked or moved slightly over time. This breakage is enough for a sewerage thirsty tree to make the drain line its new home. 
  2. The roots form a strong barrier that makes it hard for any passing matter to flow through.
  3. At first, it’s pretty unnoticeable as roots spread through the pipeline. 
  4. Eventually, things like paper and solids are caught, but water can move around, though this too eventually becomes slowed. You may notice drains beginning to slow or gurgle. around the house. 
  5. Finally, the drain is completely blocked, which is the clearest sign of a complete root drain blockage no matter is able to pass.

How Far Can Roots Spread? 

That tree in the neighbour’s yard can’t be what’s causing your blockage… or can it? Well, bad news, it could be! 

It’s pretty straightforward to figure out how far tree roots spread! Most species of tree roots will spread 2-3x the radius of the canopy. More bad news for Aussies! Roots can grow to 5x in dry conditions (which Queensland certainly has).

Quick maths. You’ve got a big tree in your yard, and the canopy radius is 3 metres. So if your soil is nice and rich, the roots may be spreading out by 6-9 metres. If the tree had to work to find water, there might be root systems as far as 15 metres from the tree. Yikes. 

How To Solve Pipe Root Blockages 

Ok, enough bad news. Let’s get into solving these issues or detecting them before it becomes a big problem. If you’re sweating after reading the last few points, fear not, we have many devices that can remove these roots until a permanent repair to the line can be carried out.

The two most common devices used by our team are our Rigid drainage eel and our high-pressure water jetter. Both devices allow us to penetrate the roots growing inside the pipe and tear them off. Although we do remove the majority of roots from the drain, they will grow back. This is why full repairs are needed – still, the treatments will give you a working sewer by clearing out the debris.

The Brisbane Metro Plumbing & Gas team can camera the drain and locate the exact spot and depth the roots are penetrating for repairs.

How To Prevent These Issues


During landscaping, make sure any trees you plant are a safe distance away from your home. If you’ve bought a property with plants nearby, consider having them removed so the roots die and won’t advance towards your home. There are still plenty of plants and trees that grow slowly with small root balls, so they won’t interfere with your plumbing down the line. 

Sometimes you don’t want to or can’t cut down a tree, so make sure to have regular camera inspections every few years to ensure there are no root blockages in your plumbing. 


Unfortunately, sometimes problems are noticed too late. This option may take time and money, but a sewer line replacement or repair offers the longest protection from root systems. Our team will highlight the source of the issue and recommend ways to replace the damaged section of pipework so the same blockage won’t happen again. 

Newly installed pipework is not fully resistant to tree root blockages either. PVC pipes are connected by glued joints and if the joints aren’t installed correctly, tree roots can easily get in. Blockages tend to occur more frequently in old earthenware (clay) pipework that is joined by large rubber o-rings. The roots like to grow through any cracks or gaps they can find.

How Brisbane Metro Plumbing Can Help

The Brisbane Metro Plumbing are experienced plumbers who can identify tree roots before they completely invade your sewer line. If you want to solve ongoing sewerage or pipe drainage issues that may be caused by roots, or simply want a check-up, contact us today. We work fast and will let you sleep easy knowing there’s not a ticking time bomb in your main sewer line.

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