What should I do first when sewage backs up?

Stop using all water immediately — every flush or tap adds to a system that cannot drain — and keep people and pets away from affected areas.

Why is sewage coming up in more than one drain?

A sewer backup blocks the main line that all your drains connect to, so multiple fixtures back up at once — unlike a single blocked fixture.

What causes sewer backups in Melbourne's south-east?

Most often tree-root intrusion in ageing clay pipes, or a collapsed section of pipe. Both need a CCTV inspection to confirm before a permanent fix is quoted.

How is a sewer backup permanently fixed?

After clearing and a CCTV inspection, the damaged section is repaired or relined so the blockage cannot reform — not just cleared and left.

Sewer Backup: What to Do Immediately, What to Avoid, and How to Get a Permanent Fix

Christopher Unwin
May 2
4 min read

Updated: Jun 13

Updated May 2026 — Around The Clock Plumbing Pty Ltd, Oakleigh South.

A sewer backup is one of the most stressful plumbing emergencies a homeowner can face — sewage rising in toilets, shower drains, or floor grates, sometimes simultaneously. Knowing what to do immediately, what not to do, and when to call for help can limit damage significantly. This guide covers the right response, step by step.

Tree root growth into a sewer drain in Oakleigh Victoria

What Is a Sewer Backup and Why Does It Happen?

A sewer backup occurs when the main sewer line serving a property becomes blocked — either by a blockage in your own drain, by a blockage in the council main that causes backflow into your property, or by a collapsed or heavily root-affected section of pipe. Unlike a localised blockage in a single fixture, a sewer backup affects all the drains in the home because they all connect to the same main line.

The most common causes in Melbourne's south-east are tree root intrusion in ageing clay pipes — roots that have been partially cleared in the past but have regrown and finally caused a full blockage — and structural pipe failure where a section has collapsed under load. Both causes require a CCTV inspection to confirm before an accurate permanent fix can be quoted.

What to Do Immediately When Your Sewer Backs Up

Stop using all water immediately. Every flush, every tap, every appliance adds volume to a system that has nowhere to drain — and increases the overflow.
Do not flush the toilet. This is the single most common mistake in a sewer backup situation — it adds a significant volume of water and raw sewage directly to an already overwhelmed system.
Keep people and pets away from affected areas. Sewage contains pathogens — E. coli, hepatitis A, and other harmful organisms. Limit exposure and clean up with gloves and appropriate disinfectant.
Check your street's kerb channel. If sewage is also appearing in the street, the blockage may be in the council main — call Melbourne Water and your council's emergency line in addition to a plumber.
Call a licensed plumber immediately. A sewer backup is an emergency — not something to leave until morning or until it 'clears itself.' It will not clear itself.

What NOT to Do During a Sewer Backup

Do not use chemical drain cleaners. They will not clear a main sewer blockage and create a chemical hazard on top of the sewage hazard.
Do not attempt to clear the blockage yourself with a hire drain machine. Without knowing the pipe condition from a CCTV inspection, an aggressive drain machine can damage a partially collapsed pipe and turn a blockage into a collapse.
Do not ignore it hoping it resolves. A partial sewer blockage that produces intermittent backflow will become a full backup. The longer it runs, the more sewage contamination you're dealing with.

What Happens When the Plumber Arrives

A plumber attending a sewer backup will first identify whether the blockage is on your side of the property boundary or in the council main — this determines responsibility. If it's on your side, the process is: high-pressure jetting to clear the blockage and restore flow, followed by a CCTV inspection to find what caused it. Fast arrival → accurate diagnosis → permanent fix. Clearing the blockage without inspecting the cause means it will happen again, possibly within weeks.

At Ronald McDonald House in April 2026, we attended a blocked sewer that had caused a backup across multiple bathrooms in the facility. We cleared the blockage, ran a CCTV inspection to confirm the cause, and had the system running normally within three hours — minimising disruption to the families staying there.

Common Questions About Sewer Backups

Is a sewer backup covered by home insurance?

It depends on your policy. Many home insurance policies cover internal water damage from a sudden and accidental sewer backup but exclude gradual damage or situations where the cause was a known pre-existing condition. Call your insurer promptly and document everything — photos before cleanup, the plumber's written report, and CCTV footage if available.

How do I know if the blockage is my responsibility or the council's?

Responsibility typically sits at the property boundary — the drain from your home to the boundary is yours; the council main from the boundary to the street is theirs. If multiple properties in your street are affected simultaneously, the blockage is almost certainly in the council main and Melbourne Water should be notified.

How do I clean up after a sewer backup?

Wear gloves and eye protection. Remove and bag contaminated material. Clean hard surfaces with a bleach solution (1 part bleach to 9 parts water). Porous materials — carpet, soft furnishings — that have been saturated with sewage generally need professional remediation or disposal. Ventilate the area thoroughly.

Can a sewer backup happen again after it's been cleared?

Yes — if the underlying cause isn't addressed. A jetting clear removes the blockage but not the root entry point or structural damage causing it. A CCTV inspection followed by pipe relining or targeted repair is the permanent fix that prevents recurrence.

Written and reviewed by Christopher Unwin — founder, Around The Clock Plumbing Pty Ltd, Oakleigh South. BPC Licence #50694, Type A gas, 22 years' experience. National Council member, Master Plumbers Australia & New Zealand.