Keeping people safe when their drinking water isn’t
Why treatment barriers are critical and consumers should take boil water notices seriously.
Generally speaking, we probably don’t think too much about our water, other than whether we have enough of it to meet our needs. Most of us enjoy the simple privilege of turning on the tap and filling a glass of quality drinking water at our leisure.
Seasonal pressures on supplies can cause significant concern, especially in rural areas where people’s livelihoods rely on having a sustainable supply. We talk about the weather a lot, and certainly we spring into action when the tap runs dry. However, for most of us, most of the time, drinking water is a ready-to-hand constant that we don’t think much about - but we should.
One important role of the Water Services Authority is to delve into the current state of our drinking water and shine a light where improvements are needed. We know New Zealand reports a disproportionately high number of E. coli detections in our drinking water compared with other countries.
The recently published Drinking Water Regulation Report identifies that there were 221 laboratory notifications of E. coli detections in 2025. 145 temporary and 88 long term Boil Water or Do Not Drink advisories were active across the country and, of the 88 supplies subject to long term advisories, 31 have been in place for more than three years. Four Directions were issued to instruct suppliers to take action to keep consumers safe, and a prosecution is currently underway following the alleged failure of a supplier to comply with the duty to supply safe drinking water.
Conducting some social research in the South Island earlier this year, staff asked rural community water supply volunteers what water meant to them. No hesitation. “Water is life!”
Simply put, we look after water, and it looks after us. That’s why the Water Services Authority – Taumata Arowai, oversees the quality and performance of New Zealand’s water networks and services.
Water is life, but contaminated water risks life. To protect public health, all the water we drink must be treated, tested and rigorously monitored to ensure supplies are safe for consumers.
We’ve put together a few questions and answers to share some ‘need to know’ safety information about our drinking water supplies.
What’s in our water
Contamination risks are many and varied. An animal drowned in the water source or the catchment tank is a visible threat. Discolouration, or turbidity, in the water or a strong odour will immediately indicate something may be amiss. But a clear, clean, fresh tasting glass of water is not an evidenced quality indicator. In fact, water that colours or has an odour or a taste might even be safer for you to drink than the glass you pour that looks, smells and tastes pristine.
It’s the invisible hazards in your drinking water we care most about, like E. coli, a type of bacteria found in the intestines and faeces (poo) of people, other mammals and birds. If E. coli is found in a drinking water sample, it indicates the water has been exposed to faecal contamination. Illness-causing micro-organisms, including bacteria, viruses and protozoa, will be in the water.
You can’t see these contaminants but, once consumed, they may show themselves in the form of stomach cramps, diarrhoea, vomiting, nausea, or fever. These gastro symptoms are unpleasant at best, and can quickly become severe, extremely dangerous or even fatal, especially for the very young, the elderly, immune-compromised, pregnant or breastfeeding mothers.
How do we keep water safe?
Safety measures for large public supplies are managed at the treatment plant and in the pipes, so we can trust the water quality at the tap. These supplies are managed by Councils and must have protozoal, bacterial and residual disinfection treatment barriers in place to protect against microorganisms that are a public health risk, causing illnesses such as cryptosporidiosis.
Smaller community supplies are often managed by volunteers, taking on the task of treatment and sampling and testing the source water and the supply and responding to evidenced contamination to protect public health.
Even smaller private supplies, like those on-farm bores servicing just a few households, must be quality-testing with treatment interventions applied to maintain consumer safety.
Why are treatment barriers important?
Ten years ago, when thousands of people got sick in Havelock North, it highlighted the importance of having not just one treatment barrier, but multiple barriers to prevent contamination.
No single barrier is effective against all types of contamination or risks. Drinking water suppliers must use a range of processes, procedures and tools to protect and treat water, to make it safe and keep it safe as it travels to the people who drink it.
Chlorine is commonly used to kill bacteria and viruses in drinking water. Chlorine provides residual disinfection, working to treat water as it journeys through the pipes, but it doesn’t protect against protozoa. Protozoa are single-celled parasites, like cryptosporidium and giardia, that can make people extremely sick. They can be removed from water with filters or managed using ultraviolet (UV) light to eliminate the health risk.
See information about chlorine
Even with UV in place and chlorine providing residual disinfection, contamination can still happen. Monitoring, sampling and testing the water supply is critical to ensure consumer safety.
People relying on untreated supplies can consider end point treatment. End point treatment options are available and reasonably affordable, designed for people to purchase and install at their house to treat their drinking water right near the tap.
Maintenance of the units is straightforward, and the kits are a great option for people wanting surety that their water is safe. Ask about them at your local Council or water service provider.
What does boiling water do?
When the drinking water supply is known to be contaminated, suppliers keep consumers safe by issuing a Boil Water Advisory. Also known as Boil Water Notices, they are an instruction put in place to ensure people can continue to drink the water while the supplier treats and stabilises the supply.
Boiling water destroys illness-causing micro-organisms like bacteria, viruses and protozoa. Science tells us that boiling your jug for the full cycle, until it is fully boiled and has automatically turned off, is enough to kill the organisms that could otherwise cause you harm.
Boiling water is intended as a temporary measure, a solution awaiting a better solution.
Why do rural supplies get hit with Boil Water Notices?
Town supplies do report E. coli detections, but it is a lot more common in rural supplies, particularly those drawing from shallow bores and where water sources are close to grazing stock.
E. coli is present in the manure and, where paddocks have a water boundary, rainwater can carry it into the source water. Even small quantities can introduce E. coli and contaminate the drinking water supply.