Water chlorination

The Council is temporarily treating Christchurch's drinking water with chlorine while it upgrades the below-ground well heads. Temporary chlorination 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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Flushing water pipes to help reduce the smell and taste

Council contractors have started flushing pipes in areas most affected by the smell and taste of chlorine.

In addition to flushing the pipes, staff are working with the appropriate health authorities to explore how we can reduce the amount of chlorine being added into the water supply.

He explains that the amount people notice the smell and taste can, among other things, depend on how close they are to the pump station. Different pump stations are used depending on demand so you may not be getting water from the one closest to you. The map below has been updated to show the location of all the pump stations.

Another factor is the condition of the pipes.

Chlorine reacts with a variety of naturally occurring materials in the pipe. It’s this reaction that can cause the variation in smell and taste in some areas and that’s why we’re flushing pipes in the worst-affected areas.

People storing water in the fridge are reminded to keep lids off containers so the chlorine can evaporate over time.

People with health issues that are experiencing increased symptoms should contact their GP.

Why there is variation in the taste and smell of water across the city

We've released some new information explaining why some people are detecting the chlorine in their water while others can barely notice it.

Through a question and answer section on Newsline, we explain that the chlorine dosing takes place at the pump station, not the individual well heads as some seem to think. From the pump station, the water flows directly out into our water reticulation system across the city. If you live close to the pump station, the chlorine dose you get coming out of your kitchen tap will be higher than if you live much further away.

The article also covers off topics such as why there is variation during the day and the impact of things like the condition of pipes on the taste and smell. It also looks at what other cities around the world do and if the situation will improve.

Council agrees on approach to well head work 

A mix of options for upgrading the security of Christchurch’s groundwater supply will be pursued so the city’s drinking water can return to its natural, unchlorinated state as soon as possible.

On Thursday April 26, the Council resolved that its preferred approach to improving well head security was to raise well heads above ground wherever practicable.

It also agreed that staff should examine options for installing UV treatment at a number of pump stations where the Council may not be able to get secure status.

The advantage of UV treatment is it doesn’t affect the taste or smell of water —most bottled water is treated this way. It can be more expensive to implement UV treatment, and unlike chlorine, it doesn’t provide protection beyond the site where treatment occurs. However, where the installation of UV treatment replaces the need to upgrade a number of well heads it can be an economical solution.

We’re hoping to reduce the amount of time we need to chlorinate. With careful management of the various pump stations as well as limiting demand where we can, we may be able to provide enough unchlorinated water for the city.

 A report will go to Council in May mapping out a draft programme for upgrading the water supply network.


Ferrymead and Lyttelton zones last areas to be treated

Temporary chlorination of the water supply in the Ferrymead and Lyttelton zones will start from 23 April 2018.

The Ferrymead zone stretches from Woolston east to Taylors Mistake and supplies 8,500 properties. The Lyttelton zone covers all the water supply zone for Lyttelton Harbour including Governors Bay and Diamond Harbour, supplying 3,000 properties.

These are the final two zones to receive temporary chlorination following on from the central zone. A single well in Wainui, servicing about 400 people, will be temporarily chlorinated from the end of April.

Read the full story

Temporary chlorination of the central zone will start during the week starting 16 April. 

About 255,000 people are in the central zone, which stretches from Sydenham to St Albans and Papanui as well as across to New Brighton in the east.


Northwest treatment brought forward

Temporary chlorination of the water supply in the northwest zone of Christchurch will begin from Friday 6 April.

The northwest zone stretches from Belfast through to Yaldhurst and includes parts of Riccarton and Addington and supplies 80,000 people. 

Map of the northwest zone

Treatment in the Riccarton zone (which is different to the northwest zone) as well as supplies in Sockburn and Hornby (the west zone) will also start from Friday 6 April.


Temporary chlorination starts in Brooklands/Kainga

The Council began the temporary treatment of the city's water supply in the Brooklands, Kainga and Spencerville area on Monday, 26 March 2018.

Following Brooklands/Kainga, which includes Spencerville, temporary treatment will be introduced gradually across the city, including Riccarton, Halswell, Parklands, the Heathcote Valley and Lyttelton Harbour.

The largest central zone will be last to be treated. It supplies 255,000 people from Spreydon and Cashmere as well as in Papanui and Grassmere and across to Linwood, Aranui and New Brighton.

It is expected that chlorination will be set up at all Council supplies in Christchurch city and Banks Peninsula by the end of April 2018.

You can call the Customer Contact Centre on 03 941 8999 or 0800 800 169 if you have any questions, or email watersupply@ccc.govt.nz

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.

Taste and smell

Initially when non-chlorinated water supplies are chlorinated you will notice a stronger smell and taste.  This will reduce over time as the chlorine breaks down the biofilm which naturally occurs on the inside of the pipes. This could take up to a few weeks depending on where you live and what pump station you get your water from. 

This is something that towns and cities that have been chlorinating their water for some time will not experience so explains why people will notice a difference compared with places they have visited or previously lived. 

The smell or taste may be more noticeable in areas close to the pump stations. Different pump stations are used to provide water on different days. This means you may notice the smell and taste more on some days and less on others,  because the water you get has travelled through different pipes to get to you, and possibly a greater distance.

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.

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 is 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 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.

Pets

Treated water is safe for household pets such as cats and dogs to drink.

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.

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 decision allows for chlorination for up to 12 months.

We are testing the chlorine levels daily from different points in the system and adjusting our dose where needed. All test results are well below the maximum set in the New Zealand Drinking Water Standards (5 parts per million). We have an agreement with the Drinking Water Assessor to dose at a rate of 1 part per million after 60 seconds contact time. This means our dosage has to be sufficient that we still maintain 1 part per million at a distance along the pipes that water travels in a minute.

We are not able to take samples on request at individual properties. 

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.

Want to know more?

Read our question-and-answer section.(external link)

Timeline to temporary chlorination

Temporary chlorination milestones

Post-earthquakes

Post-earthquakes

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.