What Dangerous Pathogens Can Get in Your Water Supply and Tank?
In New Zealand, self-supplied water tank systems—especially those collecting rainwater or drawing from bores, streams, or springs—can be vulnerable to contamination by a range of dangerous pathogens, including bacteria, viruses, and protozoa.
These contaminants can pose serious health risks if the water is not properly treated or maintained.
As the old saying goes ‘Prevention is the best cure’ and regular, professional water tank cleaning is one the best ways to keep the nasties in check.
Common Pathogens Found in Self-Supplied Water Tanks in NZ
Bacteria
- Escherichia coli (E. coli)- indicates faecal contamination; can cause severe gastrointestinal illness, including diarrhoea and vomiting. Learn how to manage the risks associated with E. Coli.
- Campylobacter – One of the most common causes of gastroenteritis in NZ; often linked to animal faeces.
- Salmonella – Can cause food poisoning-like symptoms.
- Shigella – Causes dysentery, a severe form of diarrhoea.
- Yersinia – Can lead to gastrointestinal infections.
Protozoa
- Giardia – Causes giardiasis, leading to diarrhoea, cramps, and nausea.
- Cryptosporidium – Causes cryptosporidiosis, a diarrheal disease that can be severe in immunocompromised individuals. See our Cryptosporidium blog here
Viruses
- Norovirus – Highly contagious; causes vomiting and diarrhoea.
- Rotavirus – Particularly affects children; causes severe diarrhoea.
- Hepatitis A – Affects the liver; spread through contaminated water or food.
Sources of Contamination
- Bird and animal droppings on roofs or in gutters.
- Dead animals or insects in tanks or gutters.
- Cracks or holes in tanks allowing entry of contaminants.
- Agricultural runoff, especially in rural areas.
- Ash, dust, and chemical residues from nearby activities or environmental events.
- Lead from old roof paint or flashing.
Health Risks
Contaminated tank water can lead to:
- Gastrointestinal illnesses (diarrhoea, vomiting, cramps)
- Hepatitis
- Infections that are particularly dangerous for infants, the elderly, and immunocompromised individuals. Source: healthed.govt.nz
Ministry of Health & Taumata Arowai Guidelines
The New Zealand Ministry of Health and Taumata Arowai (the drinking water regulator) recommend:
- Installing first-flush diverters, gutter guards, and mesh screens.
- Using UV filtration and sediment filters for treatment.
- Cleaning tanks and gutters regularly.
- Ensuring roofing materials are safe and free from lead-based paints. Source: healthed.govt.nz
- Regular testing of tank water for E. coli and other pathogens to check the preventative measures listed are working.
You can access the full Ministry of Health pamphlet on safe household water from tanks here: Water Collection Tanks and Safe Household Water – HealthEd.
Safe H2O have produced a series of blogs providing more detail on each of the above bacteria, protozoa and viruses that present a risk. See them all here.
If you have a worried about the safety of your water supply, need your tank cleaned or are considering filtration feel free to contact our team – we operate New Zealand wide and are here to help.