Why we chlorinate

Chlorination is one of the most effective ways to keep our drinking water safe. We add a small, controlled amount of chlorine to the water supply to kill harmful bacteria and viruses that could make people sick. This helps protect the health of everyone in the community—especially during times when the water network may be more vulnerable, like after heavy rain or maintenance work.

Chlorine remains in the water as it travels through the pipes, continuing to safeguard it until it reaches your tap. This lasting protection is one of the key reasons chlorination is used by water suppliers across New Zealand and the world.

We know some people have concerns about chlorine taste or smell, so we’ve provided additional information and resources to help answer common questions and explain the process in more detail.

Under the Water Services Act 2021, councils must provide a form of ongoing disinfection—usually chlorine—unless they’re granted an exemption by the water regulator, Taumata Arowai (for more information on an exemption, visit Exemptions | Taumata Arowai).

The following regulations and rules for chlorine have been issued by Taumata Arowai under the Water Services Act 2021.

These regulations set out the maximum amounts of substances, organisms, contaminants and residues that may be present in drinking water.

  • The Drinking Water Quality Assurance Rules - The rules provide the minimum compliance requirements to ensure the drinking water complies with the Drinking Services (Drinking Water Standards for New Zealand) Regulations 2022. The rules for chlorine vary according to the size of the population being served by the water supply.

Chlorine is added to drinking water to kill germs that can make people sick. It works by breaking down the outer layers of bacteria and some viruses, stopping them from growing and spreading.

Even after water leaves the treatment plant, chlorine keeps working as it moves through the pipes, helping to protect the water all the way to your tap.

Council’s water supplies are chlorinated at the treatment plants by dosing chlorine gas to the water flow. Other treatment processes treat water only at the point of contact. Chlorine travels with the water, which means it protects the supply right through the network so that if contamination enters via pipe breaks, cross-connections of backflow incidents, any bacteria are inactivated and cannot cause illness. Chlorine is just one part of a multi-barrier risk management approach to providing safe drinking water to our customers.

Chlorine levels are continuously monitored at our treatment plants and regularly checked at the reservoirs and throughout the network to ensure it is within safe levels.

You may notice a slight chlorine smell or taste—especially if you're not used to it. This is completely normal and shows that there’s enough chlorine in the water to keep it safe all the way to your tap. The levels used are carefully monitored to stay within New Zealand Drinking Water Standards.

If you prefer non-chlorinated water, there are several options.

You can purchase water, but this is expensive and not eco-friendly.

You can:

  • Let water stand – Fill a clean jug with water and set it aside for several hours. A jug can be placed in the refrigerator overnight while the chlorine dissipates naturally after a few hours.
  • Use a handheld carbon filter jug for your fridge. These are available from local kitchen and department stores (as well as replacement filters). The water trickles through a filter and can be used numerous times.
  • Install a water filter – granular activated carbon filters (GAC) will remove chlorine and can be cost effective for household use.

These devices can be attached to a jug, tap e.g. kitchen sink, installed under the sink or within a fridge or attached to the pipe coming into your home so that your entire household water system is filtered.

These systems are available from hardware supply stores and water filter companies. All filter replacements and maintenance need to be in accordance with the manufacturer’s instructions.

Chlorine can irritate existing skin conditions like asthma, eczema or dermatitis. If you notice your skin becoming dry or itchy, applying a moisturizer after showering or bathing can help. Should you experience increased skin irritation, asthma symptoms or other concerns, it’s important to consult your GP. You can also contact Healthline any time for free health advice on 0800 611 116.

Yes – chlorinated water is safe for most pets, including cats, dogs, and birds. If you’re unsure, it’s best to check with your vet or local pet store for advice specific to your animal.

Fish and amphibians are more sensitive, as they absorb water directly into their bloodstream. For outdoor ponds, you can let the hose run at a trickle to dilute the chlorine, or leave water to sit for 24 hours so the chlorine can naturally evaporate in sunlight.

For indoor tanks, fill a container with water and let it stand for at least 24 hours before use. Only replace about a third of the tank’s water at a time.

You can also buy de-chlorination treatments (like sodium thiosulfate) from most pet stores.

There are many reasons why pipes or hot water cylinders might leak or need replacing. These can include the natural make-up of the water, the age and type of the cylinder, and whether there’s any build-up or debris in the system.

Chlorine is just one of many factors, and it’s unlikely to be the sole cause of damage. For this reason, Council does not provide compensation for leaks or damage to private plumbing systems.