Chlorination – some commonly asked questions

Why does QLDC want to add chlorine to our 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 treatment is very effective in killing bacteria and pathogens when water enters our treatment system. What it can’t do is continue to treat the water once it is in the reticulation network (our reservoirs, pumps and pipes). Chlorine disinfects the water all the way from the intake point to your taps. It also kills small bugs that can get through filtrations systems, such as bacteria and viruses that can’t be physically removed from water.

We already have UV treatment so why do we need chlorine too?

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

There is always the potential for contaminants to get into the water reticulation system, for example through cracks in the reservoir, broken pipes – tree roots growing through pipes are a common problem, as are unlawful connections from households where people do their own plumbing.

How much chlorine will you use?

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.

I’ve heard that chlorine is unsafe – is that true?

No. Chlorine has been used safely all over the world for around 120 years. It keeps millions of people all round the world – including most of New Zealand – safe from waterborne illness.

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

You have choices.
• 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.
• Install an under-bench filter

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.

I want to tell my elected representatives what I think about permanent chlorination for my town’s water supply – what can I do?

The Council will be deciding whether or not to chlorinate after considering community feedback on the proposed annual plan for 2017-18. Please go to our Annual Plan submissions page and give your feedback by 28 April 2017. You can also email