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    Information about our water quality and our means of compliance and advice on protecting our water supply

Ensuring safer water - chlorination upgrades 2022

New Zealand’s drinking water laws have changed.

Under the Water Services Act 2021, passed in November 2021, all councils must provide residual disinfection (chlorine) for public drinking water supplies by 15 November 2022.

If you’re on a water supply that isn’t currently chlorinated then the Council will be installing the chlorination systems and running temporary chlorination, in order to comply with the law.

The planned schedule for this work is:


Chlorination to begin in the week commencing


3 October


17 October

Rakaia Huts25 October

West Melton

31 October


7 November


14 November


21 November


28 November

Jowers Road

5 December

Selwyn District Council has started applying for exemptions for public water supplies that are not already chlorinated. Selwyn was the first council in the country to file an application for an exemption from chlorination. However, where a scheme does not have an exemption on 15 November 2022, the Council is required by law to continue temporary chlorination.

Taumata Arowai has indicated it does not expect to have any exemption applications processed by 15 November 2022. See the FAQs below for more on exemptions.

Chlorination is widely and safely used in New Zealand and around the world both as a short-term treatment and as a permanent treatment to ensure protection against contamination. The majority of drinking water supplies in New Zealand are chlorinated, including nine of Selwyn’s 27 supplies.

The Council has made a major investment in recent years to upgrade all its water supplies to have a multi-barrier approach using filtration, UV treatment and other barriers at all water treatment plants. The required chlorination provides protection for water within the reticulation system (pipes) between the treatment plant and users.

Following consultation, the Council indicated as part of the Long-Term Plan 2021-2031 that we would work with Taumata Arowai to clarify the requirements for gaining an exemption and consider the costs and rating options for upgrades to gain exemptions for our supplies.

We will be continuing this process, applying for exemptions for our unchlorinated supplies on a risk basis, starting with those identified as having the lowest risk and considering the costs and rating options for upgrades to gain exemptions.

Schemes under permanent chlorination

  • Upper Selwyn Huts Water Supply
  • Dalethorpe Water Supply
  • Hororata Water Supply
  • Acheron Water Supply
  • Sheffield/Waddington Water Supply
  • Springfield Water Supply
  • Castle Hill Water Supply
  • Hartleys Road (Malvern Hills) Water Supply
  • Arthurs Pass Water Supply

Schemes under temporary chlorination

  • Tai Tapu
  • Southbridge
  • Te Pirita
  • Kirwee
  • Claremont
  • Darfield
  • Lake Coleridge
  • Dunsandel
  • Springston

Please refer to our Water Supply web page or to your Rates Information to check which water scheme you are in.

Exemption applications

The Council is applying for exemptions on a risk basis, starting with those supplies previously assessed as being at least risk.

The Council's first exemption application was for the Rakaia Huts water supply. This application is currently being processed by Taumata Arowai, including a site inspection by an international expert. The Council is preparing other exemption applications, to file in the coming months. Initial feedback from Taumata Arowai commended the Council on the thoroughness of its first application.

The Council is intent on giving each application the maximum chance of success based on feedback from Taumata Arowai, including the outcome of our first application.

Frequently asked questions

Why is my water being chlorinated?

Chlorine is used as a preventative measure against contamination because it kills the bacteria that can get into water supplies and spread disease, helping ensure supplies are safe to drink.

New Zealand’s drinking water rules are changing. The new Water Services Act 2021 came into effect on 15 November 2021 requiring all Councils in New Zealand to be able to provide residual disinfection (chlorine) for all public drinking water supplies and for all supplies to be chlorinated by 15 November 2022, unless they have an exemption from the drinking water authority Taumata Arowai.

This is to keep drinking water safe.

All water on Selwyn supplies is treated at water treatment plants before it enters the pipes to your property. Chlorination provides an additional safe, effective treatment through the pipes, all the way up to your tap.

Chlorination has been used safely and effectively all over the world for around 120 years as a preventative treatment to avoid contamination of water supplies. It keeps millions of people all round the world safe from waterborne disease, including the majoirty of New Zealanders.

When will my water supply be chlorinated? 

For supplies that are not already chlorinated, the Council is working through the process one supply at a time and we will contact you before the chlorine is turned on for your supply.

If you are on a supply that is already permanently chlorinated, then nothing will change for you.

Is it safe?  

Chlorine has been used safely all over the world for around 120 years. It keeps millions of people all round the world safe from waterborne disease.

The majority of New Zealand’s drinking water is chlorinated. In Selwyn we have nine water supply schemes that are already permanently chlorinated, providing effective treatment to keep the water safe for those communities.

The amount of chlorine added to the water supply is carefully managed to ensure levels of chlorine in the water people drink are absolutely minimised.

Chlorine levels are monitored continuously at our treatment plants to ensure the levels are safe. Monitoring equipment is also being added throughout the networks over time.

Will the Council get an exemption for my supply?

The Council has begun the process of applying for exemptions for our water supplies – to our knowledge we were the first Council in the country to apply for an exemption under the new rules.

We’re applying on a scheme-by-scheme basis for our unchlorinated supplies, using a risk-based assessment, starting with the lowest risk schemes first. As this is a new process we don’t know how long it will take to get a decision from Taumata Arowai.

If we are unable to gain an exemption for a supply then chlorination will become permanent as required by law.

We are also assessing the cost to upgrade those supplies that do not qualify for an exemption. Upgrades will need to covered by rates and the Council has committed to discussing this with our residents once we have a clearer idea of the costs to gain exemptions for our supplies.

You don't have to chlorinate until 15 November, why not wait? You're applying for exemptions why not wait to see what happens with them?

The new law gives all public drinking water suppliers in New Zealand until 15 November 2022 to ensure they have chlorination systems in place and working. This means all work must be completed before 15 November, which is the final date to ensure all systems are running.

Taumata Arowai says it does not expect to have any exemptions issued by 15 November.

The Council has 16 water supplies that were previously unchlorinated and require chlorination under the new law. We are working one supply at a time to ensure all supplies comply with the law by having the systems in place and working by 15 November.

 I can taste/smell the chlorine, why? 

In the early stages of chlorination you might notice a slight change in taste as the new treated water moves through the scheme and mixes with unchlorinated water in the Council’s reservoirs. However, most users report that this settles after the first few days.

At the minimum dose most people should not be able to smell or taste chlorine. However, the smell and taste of chlorine increases when the chlorine is consuming any organics, or when the dose is increased. So being able to smell or taste the chlorine could mean that it is doing its job of treating anything that could make your drinking water unsafe. Alternatively it could mean that the dose has been increased due to a specific situation where we’ve needed to add more to keep the water safe.

How much chlorine is being added to my water?

The new rules require that we have a minimum dosage of 0.2 parts per million (ppm) in the water when it reaches each property on the supply.

The amount of chlorine dosed into the water supply is carefully managed to ensure levels of chlorine in the water people drink are absolutely minimised. This dosage may vary at specific times if it is needed to keep your drinking water safe.

I don't want chlorinated water, how do I remove it?

You can install an under-bench filter or 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.

Chlorine and any associated by-products can be removed by using a granulated, activated carbon (GAC) filter. These are available from hardware supplies stores and water filter companies.

What to do if you don’t want to shower or wash your clothes in chlorinated water: You can buy at your own cost a filter that attaches to your water supply where it enters your property. It will remove all the chlorine from the water to your home.

The use of filters will reduce  any risks for those on dialysis. This can be arranged by the Canterbury District Health Board.

What if I have a skin condition or sensitivity to chlorine?

Chlorine can be an irritant for existing skin conditions such as asthma or eczema. If you feel your skin getting dry or itchy, use moisturiser after having a shower or bath. If you notice increased skin irritation, asthma symptoms or other symptoms, seek medical advice from your GP. To minimise exposure to chlorine, try bathing at times of low water demand – in the middle of day on weekdays, early in the morning (before 7.30am), or late in the evening (after 9.30pm).

In Canterbury, you can call your usual GP’s number after hours and your call will be put through to a nurse who can provide free health advice. You can also contact Healthline any time for free health advice on 0800 611 116.

Does chlorine cause cancer?

The International Agency for Cancer Research (IARC) does not believe chlorinated water is either a probable, or even possible, cause of cancer.

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.

The Journal of the National Cancer Institute acknowledges that “water chlorination is one of the major disease prevention achievements of the 20th century”, and that it “has become the principal means of effectively reducing waterborne enteric diseases”, which the World Health Organisation has stated account for a significant number of deaths every year, even in developed countries.

What about my pets?

If you have fish in outside ponds you will need to either turn down in-coming water to an absolute trickle (this dilutes the chlorine level to a safe amount for your fish), or fill up drums of water and let them sit for at least 24 hours before using (the UV of the sun evaporates chlorine).

For fish tanks or bowls inside, fill up a container of water and let it sit for at least 24 hours and then only replace a third of the water at a time. If you’re still worried, you can buy de-chlorinating kits (sodium thiosulfate) at pet supplies stores.

Will chlorination damage my hot-water cylinder? And will the Council pay for me to get a new one if it does?

There are multiple factors that can lead to a hot water cylinder leaking, and then needing to be replaced. These include: the chemical composition of the water, the age of the cylinder, the type of cylinder, whether there is any debris in the cylinder, and the quality and thickness of the copper used.

Because of this, the Council will not be compensating property owners where cylinders fail.

In Christchurch, where there was an increase in hot water cylinders failing after the introduction of chlorination it appears the majority of the cylinders that failed were reported as older, low pressure copper cylinders.

What are the drinking water standards?

The Drinking Water Standards for New Zealand are issued by Taumata  Arowai under the Water Services Act 2021 and set out the requirements water suppliers need to meet to provide safe water to their communities. The standards set out:

  • Maximum amounts of substances, organisms, contaminants and residues allowed in drinking water.
  • Criteria for demonstrating compliance with standards.
  • Action to be taken in the event of non-compliance with standards.