Quick answer: Treat floodwater from a drain overflow, sewage backup or outdoor flooding as potentially contaminated. Keep people and pets out, avoid electrical hazards, photograph the damage, and arrange an assessment before attempting to save porous materials such as carpet, underlay, plasterboard or insulation.
What does “Category 3 water” mean?
In restoration work, Category 3 describes grossly contaminated water, including sewage-affected water. Not every flood has the same contamination risk, so the source, affected materials and time of exposure need to be assessed. Where the source is uncertain, the safer approach is to avoid contact and treat the area cautiously.
Floodwater safety response chart
| What you find | Immediate action | Why it matters |
|---|---|---|
| Water near plugs, appliances or damaged wiring | Do not enter; isolate power only if safe and seek qualified help. | Floodwater and electricity can create a serious shock risk. |
| Sewage smell, drain overflow or unknown source | Keep the area closed off and avoid direct contact. | Contaminants may be present even if the water has receded. |
| Wet carpet, underlay, plasterboard or insulation | Document first; arrange an assessment before cleaning or drying. | Porous materials can retain moisture and contamination. |
| Flood silt and debris | Avoid sweeping or vacuuming in a way that spreads dust. | Safe removal reduces transfer to clean areas. |
First actions after contaminated floodwater
- Keep children, pets and unnecessary foot traffic away.
- Do not enter water near electrical equipment or damaged wiring.
- Take wide and close photographs before major removal or cleaning.
- Wear suitable protective clothing, gloves, eye protection and sturdy footwear if entry is unavoidable and safe.
- Wash hands and exposed skin after cleanup; seek medical advice if you are injured or concerned about exposure.
- Separate clean areas from affected rooms to avoid tracking contamination through the property.
New Zealand Civil Defence advises people to return only when it is safe, record damage, and discard items wet with floodwater that cannot be cleaned. See the official flood recovery advice for current safety information.
What may need professional assessment?
Carpet, underlay, plasterboard, insulation, skirting and porous furniture can retain moisture or contamination. A surface may look dry while moisture remains underneath or behind it. The appropriate action depends on the water source, the material and how long it was affected; do not rely on deodoriser or surface cleaning alone.
Drying comes after safety and contamination control
Once the source is stopped and the contamination risk has been considered, drying may include controlled extraction, removal of unsuitable materials, air movement, dehumidification and moisture monitoring. For guidance on the next stage, see our emergency carpet drying action plan and wet underlay guide.
Frequently asked questions
Is every flood automatically Category 3 water?
No. Category 3 refers to grossly contaminated water, while the classification of a particular loss depends on the source and conditions. If floodwater is from outdoors, a drain overflow, a sewage backup or an unknown source, avoid contact until it has been assessed.
Can contaminated carpet be cleaned?
That depends on the source of the water, the materials affected and the duration of exposure. Arrange an assessment before deciding whether porous materials can be safely cleaned, dried or need removal.
Should I use a household vacuum on flood silt?
Avoid methods that spread dust or contamination. Keep the area isolated and seek advice for significant silt, sewage contamination, mould or concealed moisture.
What should I photograph for an insurance claim?
Photograph the source where visible, affected rooms, water lines, damaged materials, contents and any mitigation work before items are removed. Keep receipts and notes of dates and conversations.
