Water chlorination

The Council is temporarily treating Christchurch's drinking water with chlorine while it upgrades the below ground well heads. Temporary chlorination will start from 26 March 2018 and provides an extra level of protection against waterborne illnesses.

Tap water in Christchurch city is still safe to drink. 

The quality of the groundwater remains excellent, and we test it daily to ensure it is free of bacterial contaminants. 

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What you need to know

Water chlorination is the process of adding chlorine to the water supply to keep it safe from harmful bacteria. Sodium Hypochlorite is used in Christchurch. It can be added as a precaution after routine work, such as reservoir cleaning, or as a result of finding bacteria in the water supply during routine water sampling.

The Christchurch water supply is made up of several zones that operate independently of each other. While the main city urban supply is being temporarily chlorinated, supplies for Akaroa, Duvauchelle, Little River and Takamatua are permanently chlorinated.

Temporary chlorination

The well heads on the groundwater wells servicing our city are no longer deemed secure. Monitoring shows there is a very small risk of contamination entering the water supply through the well heads. We are temporarily chlorinating the water supply on the advice of public health professionals because chlorination provides an extra layer of protection, just in case.

Chlorine will need to be added into the water until the Council and public health officials are satisfied the below ground well heads across Christchurch are fully sealed so there is no risk of contamination.

The Council resolved that long-term it wants to retain the city's untreated water supply system and will oppose any Government moves to impose mandatory permanent chlorination.

Temporary treatment is expected to cost about $600,000 to set up and about $250,000 a year to run.


The chlorine might be noticeable at the beginning of the treatment process but the taste will become less noticeable the further away from the pump station you are. If you are concerned about the taste, you can keep drinking water in a jug in the fridge. The chlorine taste will dissipate naturally over a few hours.

The chlorine may react with organic content in the pipes and dislodge it. That could result in some harmless organic matter coming through your taps after the initial treatment dose. The water should clear though once the tap has been run for a few minutes.

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

Health and safety

There is no health risk from drinking our tap water.

There will no need to make any changes to how you use water. There are no known health impacts from drinking water effectively treated with chlorine and it is safe for pregnant women to drink. 

The amount of chlorine dosed into the water supply will be carefully managed to ensure levels of chlorine in the water people drink are absolutely minimised.

The use of filters will mitigate any risks for those on dialysis. This is being arranged by the Canterbury District Health Board.

In a small number of people chlorine can be an irritant for an existing condition 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.


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 1/3 of this water at a time with what is in the tank already. If you’re still worried, you can buy de-chlorinating kits (sodium thiosulfate) at pet supplies stores.

Want to know more?

Read our question and answer section.(external link)

Timeline to temporary chlorination

Temporary chlorination milestones



Below ground well heads declared provisionally secure with regular assessments done.

May 2017

May 2017

The Havelock North inquiry stage 1 report is released and identifies below ground well heads as a possible source of water contamination. The Council gets its contractor to investigate the condition of its below ground well heads.

August 2017

August 2017

In response to the investigation of below ground well heads, the Council begins an improvement programme.

December 2017

December 2017

New security assessments are done and find that the well heads assessed do not meet the standard to be declared secure. The Drinking Water Assessor advises that the water supply is no longer provisionally secure.

25 January 2018

25 January 2018

Following discussions with the Canterbury Medical Officer of Health, the Council decides to temporarily treat the city’s water supply while the well head upgrade work is done. It is expected to take about two months to set up temporary chlorination.

26 March 2018

26 March 2018

The Council begins temporary chlorination of the city’s water supply.

Where have we chlorinated

Map Listing

For more information

You can email specific questions to watersupply@ccc.govt.nz or call (03) 941 8999 or 0800 800 169.