What should I do if my drain is overflowing or causing sewage to back up into my home?

If your drain is overflowing or sewage is backing up into your home, stop using all plumbing fixtures immediately, keep people and pets away from the affected area, avoid contact with contaminated water, and contact an emergency plumber as soon as possible. Overflowing blocked drains can expose your household to harmful bacteria, damage floors and walls, and quickly turn a minor plumbing issue into a costly repair if not addressed promptly.

Drain overflows and sewage backups are plumbing emergencies that should never be ignored. They often indicate a significant obstruction, damaged pipe, or overloaded drainage system that requires professional diagnosis. Understanding what to do in the first few minutes can help reduce property damage and protect your family’s health while waiting for a plumber.

If you’re unsure what causes these emergencies, read our guide on the most common causes of blocked drains in homes.

For urgent assistance, explore MPJ Plumbing’s professional blocked drain services to diagnose and clear emergency drain blockages using specialised equipment.

Why overflowing blocked drains should always be treated as an emergency

Unlike a slow-draining sink or shower, an overflowing drain or sewage backup usually means wastewater can no longer flow through the drainage system.

Instead of travelling safely into the sewer, wastewater is forced back through the lowest available outlet, which may include:

• Toilets
• Floor wastes
• Showers
• Laundry drains
• Outdoor inspection openings

Once sewage enters your home, every minute counts. Water can soak into flooring, plasterboard, cabinetry and insulation, increasing repair costs and creating conditions for mould growth.

Immediate safety steps if sewage is backing up

The first priority is protecting everyone inside the property.

1. Stop using water immediately

Do not:

• Flush toilets
• Use showers
• Run taps
• Operate washing machines
• Use dishwashers

Adding more water into the drainage system increases pressure and usually makes the overflow worse.

2. Keep everyone away from contaminated water

Sewage contains harmful microorganisms including bacteria, viruses and parasites.

Children, elderly family members and pets should stay well clear of affected areas.

3. Turn off electricity if necessary

If contaminated water is approaching electrical outlets, appliances or power boards, switch off electricity to the affected area only if it is safe to do so.

Never stand in contaminated water while touching electrical equipment.

4. Ventilate the area

Open windows and doors where practical to improve airflow and reduce unpleasant odours.

5. Call an emergency plumber

Professional equipment is usually required to identify and safely remove severe drain blockages.

What NOT to do

Many homeowners unintentionally make the situation worse.

Avoid these common mistakes.

Don’t use chemical drain cleaners

Chemical products rarely clear major sewer blockages.

They may also:

• Damage pipework
• Create dangerous chemical reactions
• Make plumbing repairs more hazardous

Don’t keep flushing

Repeated flushing simply adds more wastewater into an already blocked system.

Don’t ignore outdoor overflow points

If wastewater is overflowing outside, it still indicates a serious blockage.

Waiting often allows the blockage to worsen.

Don’t attempt to dismantle sewer pipes

Large sewer blockages require specialised equipment and experience.

DIY repairs can damage pipes and create additional health hazards.

How to minimise water damage while waiting for the plumber

Although the blockage itself requires professional attention, there are several steps you can take to reduce damage.

Move belongings

Relocate furniture, rugs and valuable items away from affected areas.

Protect timber flooring

Standing water can permanently damage timber flooring if left untreated.

Use towels or barriers

If safe to do so, use towels or absorbent materials to limit water spreading into unaffected rooms.

Photograph the damage

If significant damage has occurred, photographs may assist with insurance claims.

Why sewage backups are hazardous

A sewage backup is much more than an unpleasant inconvenience.

Raw sewage may contain harmful pathogens capable of causing illness through skin contact or accidental ingestion.

Potential health risks include:

• Gastrointestinal infections
• Skin irritation
• Respiratory problems
• Eye infections

Contaminated materials such as carpet, insulation and plasterboard may also require professional cleaning or replacement.

For health advice following sewage contamination, visit the NSW Health guide on cleaning and disinfection after sewage contamination. 

What commonly causes overflowing blocked drains?

Several underlying issues can lead to severe drain overflows.

Tree roots invading underground pipes

Tree roots naturally seek moisture.

Tiny cracks in ageing sewer pipes allow roots to enter before expanding into dense masses that restrict water flow.

Over time this often develops into a complete blockage.

Grease and food waste

Kitchen sinks are one of the most common sources of blocked drains.

Grease may appear liquid when hot, but cools and hardens inside pipes.

Combined with food scraps, coffee grounds and soap residue, it gradually narrows the pipe until wastewater can no longer pass.

Collapsed or damaged pipes

Older clay, earthenware or damaged PVC pipes may collapse due to:

• Ground movement
• Heavy vehicles
• Tree root pressure
• Age-related deterioration

Pipe collapse prevents wastewater from flowing normally.

Heavy rainfall

Stormwater systems can become overwhelmed during intense rainfall.

If stormwater drains are already partially blocked, flooding around the property may occur.

Sewer network blockages

Occasionally the blockage lies within the sewer connection rather than your home’s internal plumbing.

Professional investigation helps determine exactly where the problem exists.

Learn more from Sydney Water about property owner responsibilities for private drains and sewer connections. 

How plumbers diagnose emergency drain blockages

Professional plumbers rarely guess.

Instead, they use specialised equipment to accurately identify the cause before recommending the most effective repair.

CCTV drain inspection

One of the fastest and most accurate diagnostic methods is a CCTV drain inspection.

A waterproof camera is inserted into the drainage system to locate:

• Tree roots
• Pipe collapse
• Grease build-up
• Foreign objects
• Cracked pipes
• Joint separation

This allows repairs to target the real problem rather than relying on trial and error.

If you’d like to learn more about this technology, read our guide on How does a CCTV drain inspection work, and when is it recommended?

Clearing the blockage

Once the cause has been identified, the plumber selects the most suitable method.

High-pressure water jetting

For many severe blocked drains, high-pressure water jetting is the preferred solution.

Pressurised water removes:

• Grease
• Sludge
• Tree root debris
• Sediment
• Soap residue

Unlike temporary drain snakes, water jetting thoroughly cleans the internal pipe walls, helping reduce future blockages.

Pipe repairs

Sometimes clearing the blockage isn’t enough.

Damaged or collapsed pipes may require:

• Pipe replacement
• Pipe relining
• Excavation
• Junction repairs

Repairing the underlying fault helps prevent recurring emergencies.

Preventing future drain emergencies

Although some emergencies are unavoidable, regular maintenance significantly lowers the risk.

Good habits include:

• Never pouring cooking oil down sinks
• Using sink strainers
• Keeping wipes and sanitary products out of toilets
• Scheduling periodic drain inspections for older homes
• Addressing slow drains early
• Removing invasive tree roots before major damage occurs

Routine maintenance is almost always less expensive than emergency repairs.

For homeowners wondering when a blockage needs professional attention, our article When should I call a plumber instead of trying to unblock a drain myself? explains the warning signs.

When should you call an emergency plumber?

Seek immediate professional help if you notice:

• Sewage backing into showers or toilets
• Water overflowing from floor drains
• Multiple drains blocked simultaneously
• Strong sewer odours throughout the home
• Gurgling toilets accompanied by slow drains
• Water rising after flushing
• Outdoor inspection openings overflowing
• Stormwater drains causing property flooding

These situations rarely resolve themselves and often worsen with continued water use.

Conclusion

Overflowing blocked drains and sewage backups should always be treated as plumbing emergencies. Acting quickly by stopping water use, avoiding contaminated areas and arranging professional assistance can minimise damage to your home while protecting your family’s health.

Modern diagnostic tools such as CCTV drain inspections, combined with high-pressure water jetting and professional pipe repairs where required, allow experienced plumbers to identify the true cause of the blockage and provide a lasting solution rather than a temporary fix.

If you’re experiencing an overflowing drain, sewage backup or another urgent plumbing emergency, contact MPJ Plumbing promptly. Their experienced team can assess the situation, identify the underlying cause and restore your drainage system safely and efficiently.

Frequently Asked Questions

1. Is an overflowing drain considered a plumbing emergency?

Yes. Overflowing drains and sewage backups should be treated as plumbing emergencies because they can pose health risks, damage your home and indicate a serious blockage within the drainage system.

2. Can I still use other sinks if only one drain is overflowing?

No. It’s safest to stop using all plumbing fixtures until the blockage has been assessed. Additional water may increase pressure within the drainage system and worsen the overflow.

3. What causes sewage to come up through the shower drain?

This usually indicates a significant sewer blockage preventing wastewater from flowing normally. The wastewater then backs up through the lowest available outlet, often a shower or floor drain.

4. Will chemical drain cleaners fix a sewage backup?

Generally, no. Severe blocked drains caused by tree roots, collapsed pipes or major grease build-up usually require professional equipment such as CCTV drain inspections and high-pressure water jetting.

5. Can heavy rain cause blocked drains to overflow?

Yes. Heavy rainfall can overwhelm stormwater systems, especially if stormwater drains are partially blocked or damaged.

6. How do plumbers find the exact location of a blockage?

Professional plumbers commonly use CCTV drain inspection cameras to locate tree roots, collapsed pipes, grease build-up and other obstructions without unnecessary excavation.

7. Is sewage backup covered by home insurance?

Insurance cover varies between policies. Some insurers cover sudden accidental damage, while others may exclude problems caused by poor maintenance. Check your policy or contact your insurer for advice.

8. How can I reduce the chance of another drain overflow?

Regular drain maintenance, avoiding grease disposal into sinks, keeping unsuitable items out of toilets and arranging professional inspections when early warning signs appear can significantly reduce future emergencies.

Continue reading this series:

• How can I prevent blocked drains in my kitchen, bathroom, and outdoor drains?
• What are the early warning signs of a blocked drain before it becomes a major plumbing problem?
• Why do blocked drains keep coming back, and how can they be permanently fixed?