What Causes Blocked Drains? (And How to Fix Them)

The most common causes of blocked drains in Canberra are tree root intrusion, grease and fat buildup, foreign objects flushed down toilets, broken or collapsed pipes, and heavy rainfall overwhelming stormwater systems. Understanding what is causing your blockage is the first step to fixing it properly and preventing it from happening again.

Are Tree Roots Blocking Your Drains?

Tree root intrusion is the number one cause of blocked drains in Canberra. The city is full of mature trees, especially in established suburbs like Belconnen, Woden, and Deakin. Those roots are constantly searching for moisture, and your sewer and stormwater pipes are the perfect target.

Roots enter through small cracks or joins in the pipe and grow rapidly once inside. What starts as a hairline crack can turn into a completely blocked or even collapsed pipe within a few years. The problem is especially common in homes built before the 1990s, where earthenware or clay pipes were standard. These pipes are more prone to cracking and root penetration than modern PVC.

Signs of root intrusion include recurring blockages in the same drain, gurgling sounds from your toilet, and slow-draining sinks or showers. A CCTV drain inspection is the most reliable way to confirm whether roots are the problem and how extensive the damage is.

Is Grease and Fat Causing Your Blockage?

Pouring cooking oil, fat, or grease down the kitchen sink is one of the quickest ways to block a drain. It might flow freely when it is hot, but as it cools inside the pipe, it solidifies and sticks to the pipe walls. Over time, layers of grease build up and narrow the pipe until water cannot pass through.

The fix is simple: never pour fats or oils down the sink. Let them cool in a container and dispose of them in the bin. For drains that are already partially blocked with grease, a professional drain clean with a high-pressure water jetter will clear the buildup and restore full flow.

What Foreign Objects Block Drains?

Toilets are designed for human waste and toilet paper. Everything else is a blockage risk. The most common culprits include:

• Wet wipes: Even those labelled "flushable" do not break down like toilet paper. They catch on joints and build up quickly.
• Sanitary products: Pads and tampons should always go in the bin, never the toilet.
• Cotton buds and dental floss: These wrap around obstructions inside the pipe and create stubborn blockages.
• Children's toys: If you have young kids, this is more common than you might think. A toy dropped into the toilet can lodge deep in the pipe.
• Excessive toilet paper: Using too much toilet paper at once, especially thick or multi-ply brands, can overwhelm the pipe capacity.

Could Old or Broken Pipes Be the Problem?

Many Canberra homes built in the 1970s and 1980s still have their original earthenware sewer pipes. These clay pipes were standard for their time, but after 40 to 50 years of use, they deteriorate. Cracks, joint separation, and partial collapse are all common issues.

A broken or collapsed pipe does not just cause blockages. It can lead to sewage leaking into the surrounding soil, creating health risks and potentially undermining your home's foundations. If you are experiencing repeated blockages in an older home and clearing the drain only provides temporary relief, the pipe itself may need to be repaired or replaced.

Modern pipe relining technology means this can often be done without digging up your entire yard. A CCTV inspection will show the exact condition of the pipe and help determine the best repair method.

Can Heavy Rain Cause Drain Blockages?

Canberra's stormwater system can be overwhelmed during heavy rain events. When gutters, downpipes, and stormwater drains are clogged with leaves and debris, water has nowhere to go. This can cause localised flooding around your property and even push water back through floor drains inside the house.

Keeping your gutters clean, ensuring downpipes are clear, and checking that stormwater drains on your property are free of debris are all simple maintenance tasks that reduce the risk of rain-related flooding.

What Are the Warning Signs of a Developing Blockage?

Blockages rarely happen without warning. Here are the signs to watch for before a partial blockage becomes a complete one:

• Slow draining: Water taking longer than usual to drain from sinks, showers, or bathtubs
• Gurgling sounds: Air trapped by a partial blockage creates gurgling noises in your pipes or toilet
• Bad smells: A sewage smell coming from drains is a sign that waste is not flowing freely
• Water backing up: Water appearing in one fixture when you use another (for example, the shower draining when you flush the toilet)
• Frequent need to plunge: If you are regularly reaching for the plunger, the blockage is getting worse

When Should You Call a Plumber vs Try DIY?

A plunger can handle most minor toilet blockages. A drain strainer can prevent hair from blocking your shower drain. These are reasonable DIY measures. But there are limits to what you should attempt yourself.

Call a professional plumber if:

• The blockage keeps coming back after you clear it
• Multiple drains are blocked at the same time (this usually indicates a main sewer line issue)
• You can smell sewage inside or outside your home
• Water is backing up through floor drains
• You have tried a plunger and drain cleaner without success

Chemical drain cleaners should be used sparingly, if at all. They can damage older pipes and are harmful to the environment. For persistent blockages, a professional drain clean with the right equipment is more effective and safer for your plumbing.