Why chlorinate? | Common questions | Community suppliesFurther reading


In 2017, Queenstown Lakes District Council consulted the public on permanently chlorinating all Council-provided water supplies across the district. This was on the back of the Havelock North water contamination crisis in 2016 and after advice from Public Health South.

As a result of this consultation, water supplies for Arrowtown, Arthur’s Point, Glenorchy, Hāwea and Luggate were all elected to be chlorinated on a permanent basis. 

Wanaka and Queenstown’s water supplies are already chlorinated. 

Why chlorinate?

Supplying safe and clean drinking water is one of QLDC's core responsibilities. There is both the expectation and legal requirement that the water is safe to drink for our residents and visitors to the region. 

QLDC is obligated to learn from the Havelock North experience. An event of that magnitude in the Queenstown Lakes District would be very damaging on a local level - in terms of the effects to residents, but also seriously damaging to the region’s tourism sector. 

Drinking from an untreated water supply is much like driving without a seatbelt. While you may be safe for the majority of the time, when something adverse happens you are completely unprotected. Chlorine acts in the same way as a seatbelt – it protects those drinking from the supply from unexpected contamination events. Additional safety features are needed to protect against all possible infections, for example chlorine does not kill cryptosporidium.

Common questions

We already have UV treatment so why does QLDC want to add chlorine to the water?

We want to make sure that our families, friends and visitors don’t get sick when they drink our water. The Health Act makes QLDC responsible for providing a safe and wholesome drinking water supply and to do everything practicable to meet the NZ Drinking Water Standards.

UV (ultra violet light) treats the water where it enters our supply network and is very effective in killing bacteria and pathogens as long as the water is not turbid (discoloured). UV treatment does not treat the water once it is in our reticulation network (our reservoirs, pumps and pipes).

There is always the potential for contaminants to get into our water reticulation system, for example through cracks in the reservoir or broken pipes. These are often caused by tree roots growing through pipes and unlawful connections from households where people do their own plumbing.

This is where chlorination makes an impact - it disinfects the water all the way from the intake point to your taps, and kills small bugs that can get through filtration systems (such as bacteria and viruses that can’t be physically removed from water).

How much chlorine will be used?

As little as possible to keep your water safe. Typically we will use a dose of 0.8mg of chlorine for every litre of water. This will give a residual dose of 0.5mg per litre in what comes through your taps.

What happened in Havelock North can’t happen here, can it?

It can, and it already has.

In 1984 before Queenstown’s water was chlorinated, about 3500 people in Queenstown became ill with gastroenteritis after a blocked sewer overflowed into Lake Wakatipu near the water supply intake.

In 2012 there was an outbreak of norovirus at Cardrona where 53 people reported being ill with diarrhoea, vomiting and nausea from contaminated water.

QLDC has regularly had to issue “Boil Water” notices for local communities because testing has shown E.coli in the water.

Is chlorine safe?

Yes. Globally, chlorine has been used safely in the treatment of water for around 120 years. It keeps millions of people safe all over the world from waterborne illness (including most of New Zealand).

I hate the taste of chlorine – what can I do?

You can fill a jug of water and leave it on the bench or in your fridge overnight. The chlorine will dissipate naturally over a few hours and the taste will be gone. Under-bench filters can also help remove the taste of chlorine.

I don’t want to shower or wash my clothes in chlorinated water – what can I do?

You can buy a carbon filter that attaches to your water supply where it enters your property. It will remove all the chlorine from the water to your home. Examples include, or

Why are we chlorinating the water supplies in Arrowtown, Arthur’s Point, Glenorchy and Hāwea?

From Chief Executive Mike Theelen


  • The law requires the Council to take all reasonable steps to protect drinking water and to meet NZ Drinking water standards. The law does not specify that water has to be chlorinated per se. Chlorination is our treatment of choice. It is cost-effective, reliable and easily implemented to substantially raise the level of protection of our water supply. Chlorine is already used to treat the water supply in Wanaka and Queenstown. It’s been commonly used internationally for over 120 years.

  • It is open to people to demonstrate alternative means by which we could meet the Drinking Water Standards and provide a safe, secure water supply. These would have to be proven to be as effective and affordable as chlorine.

  • There are severe legal risk and possible penalties for the Council if we fail to take reasonable steps.

  • We are no less liable today than the Council has been for many years. QLDC has not acted consistently to date. Previous Councils and management have chosen not to provide a higher standard of water treatment despite this being on our water management plans for some time. Council has allocated funding to implement chlorination as the preferred method of treatment forthwith, to put all public supplies on an even footing.

  • We also need to be mindful that adding Chlorination and UV treatment will not get us to meet Drinking Water Standards, which requires ongoing work.

  • While the advice of the specialists is that chlorine is very effective, there always remain to opportunity for alternative methods to be implemented should they become available and cost effective in the future. I do not think that opportunity should be discounted but neither to I consider that it prevents a safe and effective solution from being applied now.

Further reading