Sewage Backup Health Risks: Why Professional Clean-Up Matters

What's actually in raw sewage

Sydney Water's warning is blunt: wastewater contains harmful microorganisms — bacteria, viruses and protozoa — that can cause illnesses like gastroenteritis if you have direct contact with it. US occupational health guidance archived by the CDC names the specific organisms sewage can carry: bacteria including E. coli, Salmonella and Shigella; viruses including hepatitis A; and parasites including Giardia and Cryptosporidium — causing intestinal, lung and other infections with diarrhoea, fever, cramps and vomiting.

The World Health Organization links exposure to human excreta with transmission of cholera, dysentery, diarrhoeal disease, typhoid, intestinal worms and polio, and notes that waterborne hepatitis A outbreaks are usually associated with sewage-contaminated water. NSW Health also lists sewer workers among the occupations at higher risk of leptospirosis — a bacterial disease that enters through cuts or the lining of the mouth, nose and eyes, and in severe cases can cause kidney failure and jaundice.

Category 3: the industry's most serious water classification

The ANSI/IICRC S500 Standard for Professional Water Damage Restoration defines Category 3 water as grossly contaminated water that can contain pathogenic, toxigenic or other harmful agents and can cause significant adverse reactions in people who contact or consume it. Its first example is sewage — and notably, the standard classifies waste line backflows originating from beyond any trap as Category 3 regardless of how the water looks. Clear-looking water from a sewer backflow is still black water.

That classification drives everything about the clean-up: protective equipment, containment, what can be salvaged, disinfection, and drying — a very different job from a burst clean-water pipe. (For the full three-category system, see our guide to the first 24 hours after a flood.)

What has to be thrown away

Australian health departments are consistent on this. Saturated porous materials that can't be effectively cleaned should be removed and discarded — because, as WA Health explains, they become reservoirs for the growth of microorganisms. That typically means:

• ✓ Carpets and underlay soaked by sewage
• ✓ Mattresses, upholstered furniture and soft toys
• ✓ Affected plasterboard and insulation
• ✓ Any food or medicines that contacted wastewater — plus leafy vegetables and soft-skinned fruit from affected gardens

Hard, non-porous surfaces can be salvaged with proper disinfection: Victorian health guidance specifies a chlorine solution of one cup of household bleach per 10 litres of water, left wet on the surface for 10 minutes and then rinsed, with good ventilation while everything dries.

If it happens to you: the safe response

• ✓ Keep people out — especially children and pets (Sydney Water's first advice for any wastewater overflow)
• ✓ Assume contamination — WA Health's rule: assume any surface or material touched by wastewater is contaminated
• ✓ Protect yourself — rubber gloves, boots, eye protection and a mask; waterproof dressings over any cuts; wash hands and face with soap and warm water afterwards
• ✓ Report network overflows — if the overflow comes from Sydney Water's network, report it on 13 90 90; Sydney Water cleans up overflows from its own network and only removes warning signs once testing confirms the site is safe
• ✓ Prevent the next one — the common causes are tree roots in pipes, flushed wet wipes, and fats and oils poured down drains

Where professional clean-up fits

For anything beyond a very small, contained spill on hard flooring, a Category 3 event inside a home is a job for certified biohazard technicians: extraction of sewage and contaminated water, removal and lawful disposal of saturated porous materials, decontamination and antimicrobial treatment of the structure, odour neutralisation, and structural drying to prevent the mould problem that otherwise follows. That's exactly what One Prime's sewage clean-up service does across Greater Sydney and Regional NSW, 24/7 — restoring the property to a condition that's safe to live in, not just one that looks clean.

Frequently asked questions