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Information about chlorine and discoloured waterNgā Pātai e Kaha Whiua Ana

Why is our water chlorinated? Pertinent answers to questions about why Napier’s drinking water supply is now chlorinated and what causes dirty water.

Information about chlorine and dirty water

The Havelock North Drinking Water Inquiry made a number of recommendations to improve safety of New Zealand’s water supplies and changes to our Drinking Water Standards.

The Government has identified that illness from the country’s public water supplies is significant, with up to 100,000 people getting sick every year. The uncomfortable reality is that New Zealand's water networks have probably been housing dangerous pathogens (bugs) for years.

Two of the main outcomes for Napier from the Havelock North Inquiry have been:

  • The raising of bore heads above ground level to stop surface water entering the bore and potentially contaminating the water.
  • Chlorination of the pipe network following seven minor contamination issues in our reservoirs and pipe system.

The water we extract from the Heretaunga Plains Aquifer is of a very high quality, however, like the majority of other public water supplies, our network is at risk of becoming contaminated. One of the ways to reduce this contamination risk is to have disinfection in the network, and this is provided by chlorine.

Supplying safe and clean drinking water is a core responsibility of Council. The community expects this and Council has a legal requirement to provide water that is safe to drink for our residents and our visitors to Napier.

We need to take into account the learnings from Havelock North to ensure that a similar event doesn’t happen here.

Drinking from an untreated water supply (without having one designed appropriately to be chlorine free) is like driving without a seatbelt. It is safe most of the time, but you need the seatbelt in the event of an emergency. Chlorine acts a little like a seatbelt.

Chlorine has been proven to be the most effective treatment for water supply networks for two main reasons:

  • It treats the water for pathogens (bugs).
  • It disinfects the pipes and reservoirs.

It is very likely that upcoming changes to the Drinking Water Standards will require a “disinfection residual” in New Zealand’s water supplies. It may soon be mandatory that our supply system is chlorinated.

We use as little chlorine in our supply as we possibly can. Typically we like to keep the dosing rate between 0.4mg/L to 0.6mg/L, but the dosing rate can be raised up to 0.8mg/L depending on the residual chlorine level in the pipe network. Currently we have differing levels of chlorine at different properties. The aim is for a chlorine “residual” of above 0.2mg/L to combat any pathogens that get into the supply.

The chlorine used to disinfect our supply is added in very low doses. Chlorine has been used worldwide for over 120 years to keep millions of people safe. Some countries have been concerned about the potential health impacts of distribution by-products. We test our network six monthly and have not detected distribution by-products.

We have a moral and legal requirement to keep people safe and to meet current legislation. Part of these requirements involve developing a Water Safety Plan that identifies the risks in our water supply and how we manage them. We use chlorine to manage the risks in our supply (mainly the risk of contamination in our network).

Also, the current stance of the newly established drinking water regulator in New Zealand (Taumata Arowai) is that all water supplies must have a residual disinfectant in order to ensure protection of public health. While water supply entities can apply for an exemption to move to a chlorine free supply, they are required to provide evidence to demonstrate that public health will not be compromised. On this basis, PDP and their international partners have developed a pathway for NCC to move towards a chlorine free future through the exemption process outlined in the Water Services Bill. However, this is not a quick fix and there is no option to go back to the way things were.

The report shortlists three options which are developed in detail:

  • Status Quo (SQ) – Making changes to bore holes, UV disinfection on all bores and upgrade existing chlorination systems.
  • Status Quo Plus (SQ+) – Improving network operations and service reservoirs, reducing leakage, increased water quality monitoring, water hygiene practices, UV disinfection on all bores and upgrade existing chlorination systems.
  • Chlorine Free (CF) – Providing a safe water supply without chlorine following the Dutch model.

The Review has developed a programme of activities that outline a staged approach in moving from the SQ position through to chlorine free. This involves a series of projects aimed at improving our understanding of how the water network is performing and reducing the public health risks associated with supplying safe and sustainable drinking water to Napier.

Council resolved in December 2019 to proceed with a review into what it would take to make Napier’s drinking water Chlorine Free. In May 2020, Council engaged Pattle Delamore Partners (PDP) to complete the review report, which we released in March of this year. The review report examines the current state of Napier’s water, looks at examples of overseas best practice, and presents a roadmap for Napier to become chlorine free.

The estimated cost for the three options is as follows:

  • Maintaining the Status Quo (SQ) position is estimated to cost $178 million over a 20-year period.
  • Status Quo Plus (SQ+) will cost $221 million over 20 years.
  • Moving to a Chlorine Free (CF) position will cost $284 million over 20 years.

Moving to Chlorine Free will also require an ongoing commitment of $4.8M per annum in pipe maintenance and renewals.

Moving to a safe, chlorine free network will take time and resources and all options will need a significant amount of investment.

More than $150 million, and it wouldn’t necessarily make it safer – there could still be breaches to the pipework from accidental and intentional breakages, and illegal connections. A complete replacement would need to be done in stages to minimise disruption. This would take more than a decade and would add significant increases to rates without the desired benefits and reduction in health risks.

We have many drinking water projects planned and underway. You can read more details about them here.

  • Three bores have been brought above ground
  • Upgrades have been made to underground bore chambers to make them safe
  • Close down of two bores that didn't meet requirements
  • Improvements to water reservoirs
  • Introduction of chlorine treatment at the source
  • Increased planned maintenance of the supply system including extensive mains cleaning projects to remove biofilm (the accumulation of organic and inorganic matter attached to the insides of pipes and water storage tanks) from our water network.

Any of the examples below could result in contaminants being introduced into our water supply network:

  • At the source or aquifer or through private bores.
  • Backflow (reverse flow) from houses or industry.
  • Damage to the pipes (eg. during excavation work or through vandalism, or asset failure).
  • Illegal access to water from fire hydrants.
  • Illegal connections to the water network.
  • Through pests and birds entering storage reservoirs.

Our water source, the Heretaunga Aquifer, has naturally occurring manganese - one of the most abundant metals in the earth's crust. When manganese-laden water mixes with oxygen or chlorine, the manganese oxidises or changes state to manganese dioxide, a black solid that can coat the inside of pipes.

Manganese has always been present in our water network. Dirty water is now more of an issue due to the manganese reacting with the chlorine we've been adding to our water since 2017. 

In Napier, this affects certain suburbs (Tamatea, Onekawa and Pirimai) more than others because of different water pressure and flow rates, and because there are higher levels of manganese in the aquifer bores that supply these suburbs.


Napier's source water has a manganese level of less than 0.07 mg/L, well below the manganese Maximum Acceptable Value of 0.40 mg/L. This is safe to drink.

The discoloured water some households occasionally experience shouldn’t be consumed as it is higher in manganese. If you do drink discoloured water it won’t cause health issues and washing in it won’t harm your skin. It may leave an oily film on your skin, which is biofilm that’s been dispersed in the water. It feels unpleasant but it is harmless.

Open your outside tap until the water colour clears. If it doesn’t clear after 15 minutes, phone our Customer Service Centre on (06) 835 7579. To help with water conservation, don't let the taps run for more than 15 minutes. Please call us if the water hasn't run clear after this time.

If you do resolve the problem yourself, we'd really appreciate a heads up that you've had problems. Please complete the 'Report It' form.

If you are unhappy with the taste of the chlorinated water, you can leave the water in a jug for a few hours and the chlorine will dissipate. Bench top jug filters are also useful.

If you experience a very strong chlorine smell, similar to a swimming pool, this generally indicates that the chlorine is doing its job, not that there is a really high level of chlorine in the water. We need to know if you have a really strong chlorine smell so that we can check it out.

You can call us on our Customer Service Centre on (06) 835 7579 or complete the 'Report It' form.

If you've experienced dirty water issues in the past, we'd recommend you run your laundry tub taps first before you do your washing. If your water isn't running clear, then run your outside tap hard for up to 15 minutes. If things still look murky, then call our 24/7 Customer Service number - 0800 4 NAPIER - and we'll send our team out ASAP. To help with water conservation, don't let the taps run for more than 15 minutes. Please call us if the water hasn't run clear after this time.

We have two de-chlorinated water station's in Napier.


  • Marine Parade, next to the National Aquarium of New Zealand.
  • Anderson Park, Greenmeadows (141 York Ave)

Napier City Council agreed to provide the community with two de-chlorinated water stations when the Long Term Plan 2018-28 was adopted in June 2018.

A cheap and simple way to deal with this is to fill a jug of water and put it on your bench or in your fridge for a few hours. The chlorine will dissipate naturally. You can also get a bench top filter jug which is very affordable or get an under bench filter to help remove the taste of chlorine.

For washing and showering, there are shower filters or full householder filters that can be purchased. Some examples are:

We investigated this option in preparing the report. The ongoing costs have been found to be prohibitively expensive and the annual replacement of the UV bulbs and cartridges presents an environmental challenge. Further the national water regulator (Taumata Arowai) would require samples to be taken for at least annual testing – further increasing the costs. Finally, the adoption would have to be community-wide otherwise the investment in the treatment would still be required to ensure a safe water supply.


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