Blocked Drains: Causes, Warning Signs and How Much It Costs to Fix in 2026

Blocked drains are the most common plumbing call we get across all 13 locations. They range from mildly annoying — a slow-draining sink — to a genuine emergency, like sewage backing up through the floor waste.

Knowing what causes them, how to spot one early, and what a professional fix actually involves helps you make the right call before a small problem turns into a big one.

What causes blocked drains?

• Grease and fat — the most common cause in kitchen drains. Cooking fat is liquid when hot and coats the inside of the pipe as it cools, building up over months into a full blockage.
• Hair and soap scum — the main culprit in bathroom and shower drains. The two combine into a mass that traps everything else.
• Tree root intrusion — roots find their way in through cracks or joints in clay sewer pipes, then grow fast enough to block the pipe entirely.
• Foreign objects — wet wipes (including the “flushable” ones), cotton pads, kids’ toys and anything else that gets flushed or dropped in.
• Structural pipe damage — cracked, collapsed or offset pipes in older homes create catch points where debris piles up.
• Mineral scale — in hard water areas, calcium and magnesium build up inside the pipe over years, narrowing it and catching debris.

Warning signs of a blocked drain

• Water draining slower than usual from one or more fixtures
• Gurgling from the drains after you’ve used water
• Bad smells coming up the drain
• Water backing up into a nearby fixture — the shower fills when the toilet flushes
• Several drains failing at once, which points to a main sewer blockage

How plumbers clear blocked drains

Blocked drain cost guide – Australia 2026

FAQs about blocked drains

Can I clear a blocked drain myself?

For a mild bathroom blockage, a drain snake or a baking soda and vinegar treatment might do it. For kitchen grease, sewer blockages or anything on the main drainage line, call a licensed plumber. Off-the-shelf drain chemicals can damage pipes and rarely deal with the underlying cause.

How do I know if it’s the main sewer line or just one drain?

If one drain is slow, it’s usually that branch. If several drains or toilets fail at the same time, the main sewer line is blocked — stop using water and call a plumber straight away.

Is a blocked drain covered by home insurance?

Generally no. Home insurance covers sudden damage like a burst pipe, not maintenance issues like blocked drains, and tree root damage to underground pipes is often excluded outright. Check your policy.