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Blocked Drains Guide

Blocked Drain? Causes, Fixes and When to Call a Plumber

What's actually blocking your drain, which fixes are safe to try yourself, and the warning signs that mean it's time to stop DIYing and call a professional.

Updated April 2026 8 min read

What causes blocked drains?

Most blocked drains don't happen overnight — they build up gradually until water won't drain at all. Knowing the cause helps you choose the right fix and avoid making things worse.

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Hair & soap scum

The most common cause in bathrooms. Hair binds with soap residue and gradually narrows the pipe until nothing gets through. Shower drains and bathroom sinks are most affected.

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Grease & food scraps

Cooking oil and fats solidify as they cool in pipes. Combined with food particles, they build a sticky layer that catches everything else. Kitchen sinks are the main victim.

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Tree roots

Roots are drawn to the moisture in sewer pipes and can infiltrate tiny cracks, growing until they cause major blockages. More common in older homes with clay or concrete pipes.

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Foreign objects

Wet wipes (even "flushable" ones), cotton buds, nappies and kids' toys are frequent culprits. These don't break down and can cause sudden, complete blockages.

DIY fixes to try first

For minor blockages in a single drain, these steps are safe to attempt before calling a plumber. If none of them work — or if the blockage affects more than one drain — skip straight to calling a professional.

1

Remove visible debris by hand

Put on rubber gloves and pull out any hair or debris you can see or reach around the drain cover. This alone fixes a surprising number of slow bathroom drains. Clean the drain cover while you're at it.

2

Boiling water (kitchen sinks only)

Pour a full kettle of boiling water slowly down a blocked kitchen sink. This can melt grease build-up. Don't use boiling water on PVC pipes or porcelain fixtures — use very hot tap water instead. Repeat two or three times.

3

Baking soda and white vinegar

Pour half a cup of baking soda into the drain, followed by half a cup of white vinegar. Cover the drain and leave for 30 minutes, then flush with hot water. Effective for mild grease and organic build-up.

4

Plunger

Use a cup plunger (flat bottom) for sinks and showers. Cover the drain fully, push down firmly and pull up sharply — repeat 10–15 times. Make sure there's enough water in the basin to create suction. A flange plunger works better for toilets.

5

Drain snake (plumber's auger)

Available from hardware stores for around $20–$60. Feed the snake into the drain until you feel resistance, then rotate the handle to break up or hook the blockage. Effective for hair clogs that a plunger can't shift. Don't force it — you can damage plastic pipes.

Avoid chemical drain cleaners. Products like Drano contain caustic chemicals that can corrode older pipes, damage seals and create dangerous fumes — especially if mixed with other products. They also rarely fix deep blockages, just push the problem further down. Use them only as a last resort before calling a plumber, and never after using baking soda and vinegar.

When to stop DIYing and call a plumber

Some blockages are beyond DIY — and attempting to fix them without the right tools can cause expensive damage. Call a licensed plumber if you notice any of these:

Multiple drains are blocked at once — if your toilet, shower and sink are all slow or blocked, the problem is in the main sewer line, not individual drains.

Water backs up in unexpected places — flushing the toilet causes water to appear in the shower, or running the washing machine backs up a kitchen sink.

Gurgling sounds from drains or toilets — a sign of a partial blockage somewhere in the system that air can't get past properly.

Sewage smell coming from drains — indicates a deep blockage or a broken seal somewhere in the system.

DIY attempts haven't worked after two tries — continuing risks pushing the blockage deeper or damaging pipes. Cut your losses and call a professional.

CCTV drain inspection: If you have recurring blockages or suspect tree root damage, ask your plumber for a CCTV camera inspection ($150–$350). It shows exactly what's causing the blockage and where — so you're not paying for guesswork.

How much does it cost to unblock a drain?

Prices vary depending on the severity, location and method required. Here are typical ranges across Australia:

Method / Job Typical Cost When It's Used
Basic drain clearing (snake / plunger) $150 – $300 Simple blockages in sinks, showers
High-pressure water jetting $250 – $500 Stubborn grease build-up, deep blockages
CCTV drain inspection $150 – $350 Recurring blockages, tree root investigation
CCTV + high-pressure jetting $350 – $700 Unknown blockage + clearing combined
Tree root removal + pipe repair $500 – $2,500+ Root intrusion with pipe damage
Emergency after-hours call-out Add $150 – $300 Weekend, night or public holiday

How to prevent blocked drains

A few simple habits prevent the vast majority of household blockages:

  • Fit a hair catcher in every shower and bath drain — clean it weekly. These cost $5–$15 from any hardware store and are by far the easiest prevention measure.
  • Never pour cooking fat or oil down the sink. Let it cool, scrape it into a container and put it in the bin. Even a small amount weekly will build up over months.
  • Only flush toilet paper — nothing else. "Flushable" wipes do not break down in Australian sewer systems and are a leading cause of blockages.
  • Flush drains with hot water weekly — after doing the dishes is ideal for kitchen sinks.
  • Have your sewer line inspected every 3–5 years if you have large trees anywhere near your property. Catching root intrusion early is far cheaper than dealing with a full blockage.

Frequently asked questions

Yes, for minor blockages in a single drain. A plunger or hand-operated drain snake from a hardware store ($20–$60) can clear most hair and soap scum blockages. If you've tried twice and the drain is still blocked, or if multiple drains are affected, call a licensed plumber — you risk making the problem worse.
Most blocked drains cost $150–$500 to professionally clear. A simple blockage with a plunger or snake is at the lower end ($150–$300). A high-pressure water jet for a stubborn or deep blockage costs $250–$500. If a CCTV inspection is also needed, add $150–$350 on top. Emergency after-hours work adds a further $150–$300 call-out surcharge.
Use them with caution. Chemical cleaners can damage older metal pipes and PVC, and the fumes are hazardous. They also rarely fix deep blockages — they may partially clear it only to have it return quickly. Never mix chemical cleaners with other products, and never use them after baking soda and vinegar. For persistent blockages, a plumber's mechanical methods are safer and more effective.
Signs include slow-draining toilets and sinks across the whole house, gurgling sounds from multiple drains, outdoor drain inspection points that fill with water, and recurring blockages even after professional clearing. A CCTV drain camera inspection ($150–$350) will confirm it definitively — it's worth doing if blockages keep coming back.
High-pressure water jetting (also called hydro-jetting) uses a powerful water jet to blast blockages clear and clean the pipe walls. It's more thorough than a snake and removes grease build-up from the pipe walls, not just the blockage itself. You'll need it for stubborn grease blockages, tree root intrusion, and situations where a snake hasn't worked. It costs $250–$500 and leaves your pipes much cleaner than alternative methods.

Drain still blocked?

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