Blocked Drains? 10 Causes Every Australian Homeowner Must Know

Blocked drains never give you a polite heads-up.
One day, your sink is slow. Next, your bathroom smells like a swamp, and the toilet is threatening to revolt.

If you live in Australia, blocked drains aren’t a matter of if; they’re a matter of when.

After clearing thousands of blocked drains across Newcastle, Canberra, the Central Coast, Lake Macquarie, Hunter Valley and Port Stephens, our plumbers see the same causes again and again. Some start small. Others quietly destroy pipes underground until one day… everything stops.

Here are the 10 most common causes of blocked drains, and what you can do before a minor inconvenience turns into a four-figure plumbing nightmare.

Grease Buildup in the Drain

1. Grease

Grease might look harmless when it’s warm, but inside your pipes it cools and sticks to the walls like glue. Over time, it builds layer after layer until water can barely squeeze through.

How to prevent it

  • Never pour grease, oil, or cooking fat down the sink
  • Wipe pans with paper towel before washing
  • Use a sink strainer

How to fix it

  • Flush hot water with dishwashing liquid
  • Try a vinegar and hot water flush
  • If it keeps coming back, a plumber needs to clear it properly
Grease & Fat

2. Fat Build-Up

Fat comes from food waste, soaps, cooking oils and even human waste. It forms thick, waxy blockages that trap everything behind them.

How to prevent it

  • Don’t rinse food scraps down the sink
  • Use fat-free or low-residue soaps
  • Scrape plates into the bin before washing

How to fix it

Fat blockages usually need professional water-jetting to remove completely.
Blocked Drains due to Hair

3. Hair

Hair tangles together, catches soap scum and creates thick clumps that block bathroom drains. We’ve pulled out hairballs metres long, no joke.

How to prevent it

  • Use a drain cover in showers
  • Brush hair before bathing
  • Clean the drain monthly

How to fix it

  • Try hot water and drain cleaner
  • Use a drain snake
  • Call a plumber if it keeps blocking
Toilets Full of Toilet Paper

4. Wipes, Sanitary Items & Toiletries

Baby wipes, tampons, paper towels and “flushable” wipes do not break down properly. They jam inside pipes and create rock-solid blockages.

How to prevent it

  • Only flush toilet paper
  • Keep a bin in every bathroom
  • Teach kids what not to flush

How to fix it

  • Try plunging
  • If the blockage is deep, CCTV inspection and extraction is required
Man Using Water Jetter

5. Tree Roots

Tree roots are the number one cause of blocked drains in Australia. They find tiny cracks in pipes and grow inside, feeding on moisture and waste.

How to prevent it

  • Have sewer pipes inspected every few years
  • Avoid planting large trees near sewer lines

How to fix it

Roots must be cut out using high-pressure water jetting and then the pipe relined or repaired.
Cleaning Roof Gutters

6. Leaves & Storm Debris

Gutters and stormwater drains fill with leaves, twigs and dirt. During heavy rain, this debris washes down and blocks the pipes.

How to prevent it

How to fix it

Blocked stormwater drains require professional flushing and inspection.

Plastic Cup Blocking A Toilet

7. Foreign Objects

We’ve found toys, toothbrushes, cloths and even mobile phones inside pipes. Once lodged, they trap waste and cause full blockages.

How to prevent it

  • Keep small items away from toilets
  • Use storage trays in bathrooms

How to fix it

CCTV drain inspection is needed to locate and remove the object safely.
Plants & Dirt

8. Heavy Rain & Flooding

Stormwater can overwhelm old or damaged drains, forcing water backwards into homes.

How to prevent it

  • Fix slow drains immediately
  • Inspect stormwater drains before storm season

How to fix it

Call a plumber immediately to locate and clear the obstruction.
A Plumber Getting Ready for a Plumbing Job

9. Broken or Collapsed Pipes

Ground movement, age and tree roots can crack or collapse pipes. These create ledges that catch waste until the pipe blocks completely.

How to prevent it

  • Get old plumbing inspected
  • Watch for damp patches or sewer smells

How to fix it

Pipe relining or replacement is required.
Plumbers Working on the Broken Drain

10. Poor Plumbing Installation

Pipes laid at the wrong angle or size will never drain properly. Water slows, solids settle, and blockages form.

How to prevent it

How to fix it

Regrading or relaying the pipe is the only permanent solution.

Blocked Drains Don’t Fix Themselves

 A slow drain today can become sewage backing up through your home tomorrow, damaging floors, walls and your health.

At The Plumbing & Electrical Doctor, we use:

  • CCTV drain cameras
  • High-pressure water jetting
  • Trenchless pipe relining

to fix blocked drains properly, not just push the problem further down the line.

We service Newcastle, Canberra, the Central Coast, Lake Macquarie, Hunter Valley and Port Stephens with fast response times and upfront pricing.

Call now or book online and get your drains flowing again before it turns ugly.

Frequently Asked Questions (FAQs)

What are the first signs of a blocked drain?

Slow draining sinks, gurgling noises, bad smells, and water backing up are all early warnings. If more than one drain is affected, the blockage is likely in your main sewer line.
Small surface blockages can sometimes be cleared with hot water or plunging. However, recurring or multiple blocked drains usually mean a deeper issue that requires professional equipment.
The most common causes are grease, fat, wipes, hair, tree roots, broken pipes and storm debris, especially in older properties and leafy suburbs.
Yes. In Australia, tree root intrusion is one of the leading causes of blocked sewer drains due to older clay pipes and large established trees.
It depends on the cause and severity. Simple blockages are often cleared quickly, while tree roots or collapsed pipes require CCTV inspection and specialist equipment.

We provide blocked drain services in Newcastle, Canberra, Central Coast, Lake Macquarie, Hunter Valley and Port Stephens.

THE DOCTOR GETS IT DONE

• Licensed & Local • Fast, Reliable Service • 24/7 Emergency

Speak to a Plumber – 13 10 91

General Plumbing & Electrical | Hot Water Systems | Blocked Drains | Gas Fitting & more. .