10 Common Causes of a Blocked Drain (and How a Plumber Fixes Them)

Blocked drains can be inconvenient, messy, and costly if not dealt with quickly. Some causes are unavoidable, while others come down to everyday habits. Knowing the common culprits can help you prevent issues—or at least understand when it’s time to call a blocked drain plumber.

1. Tree Roots

Tree roots are one of the leading causes of blocked drains in Australia. Once they infiltrate a pipe, they trap debris and restrict flow. This problem requires professional intervention—if you notice slow drainage without an obvious cause, contact a qualified plumber for inspection and repair.

2. Storm Debris

Heavy rain can wash leaves, twigs, and mud into stormwater drains, leading to blockages. While you can’t prevent storms, a professional plumber can clear the system quickly and restore proper flow.

3. Old Pipes

Ageing pipes naturally deteriorate, often narrowing with years of buildup or cracking under pressure. If your property has old plumbing, replacement may be the only long-term solution. Upgrading incoming pipes at the same time ensures a reliable water supply.

4. Broken Pipes

Pipes can break due to ground movement, poor installation, or root intrusion. Cracks catch debris, eventually creating a blockage. Depending on the damage, a plumber may reline the pipe or recommend a replacement.

5. Poor Installation

Substandard plumbing work or low-quality materials can lead to recurring blockages. A professional plumber can assess the system and either repair faulty sections or replace the entire installation if necessary.

6. Foreign Objects

Toys, excessive toilet paper, and other household items—often courtesy of curious children—are common causes of blockages. While prevention is difficult, educating your family about what shouldn’t go down the drain can help.

7. Nappies and Sanitary Items

These products swell when exposed to water, making them major contributors to clogged drains in both homes and businesses. Always provide a bin for disposal and avoid flushing them. If a blockage occurs, you’ll need a blocked drain plumber to clear it.

8. Hair Buildup

Hair naturally collects around shower and bath drains. Regularly cleaning the plughole prevents clumps from reaching deeper into the system. For stubborn buildup, schedule drain maintenance with a professional.

9. Soap Scum

Certain soaps and body washes leave behind residue that builds up in pipes. Eco-friendly, low-foam alternatives can reduce this risk, while regular cleaning and maintenance keep drains clear.

10. Grease and Fat

Pouring cooking grease or oil down the sink leads to solidified blockages once it cools inside the pipes. Dispose of fats in the bin instead. Minor buildup can sometimes be managed with boiling water or vinegar, but persistent issues require professional cleaning.

If you suspect a blockage or can’t resolve one yourself, don’t wait for the problem to worsen. Contact Mainline Plumbing and our experienced team will have your drains running smoothly again in no time.