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Information about chlorine and dirty 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 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 each person’s house, 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 supply and how we manage them. We have Chlorine as a way to manage the risks in our supply (mainly the risk of contamination in our network).

If we switch the chlorine off with no change to the way that we manage risks we would be non-compliant and potentially be subject to enforcement action. But mostly, we want to keep people safe and will meet our legal requirements.

We have a review underway with a consultant to look at two main options for our community.

  1. Continuing with Chlorine free and upgrading our network, maintenance practices, risk management and monitoring etc with chlorine disinfection. Called “Status Quo Plus”
  2. Providing a safe water supply without chlorine.

We will present the potential options for chlorine free to our Councillors before we choose a preferred chlorine free option to compare against the “Status Quo Plus” option. This will let us know what work we need to provide a safe, modern, compliant network with or without chlorine, what the changes will be to our capital plan, our maintenance work and the costs to do this and the time it will take to do the work.

We have local and international experts looking at these options for us and they will work with the Council, and the Ministry of Health to provide the best options going forward.

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

There are three main options that we could look at:

  1. Remove chlorine and accept the risk
  2. Continue to manage risk with chlorination
  3. Change our network to remove chlorine and minimise risks (Netherlands model)

Both the Hawke’s Bay District Health Board (our Drinking Water Assessor) and Napier City Council are not willing to risk lives by removing chlorine from the water. Chlorine is the most cost-effective, efficient way to minimise contamination risks in our network.

To bring the Netherlands model to Napier we would need to reduce network leakage from our current 22% (typical for a water network like ours) to less than 5%. We would need to replace large parts of our network (potentially 55% at $72m), and add extensive monitoring and control infrastructure (several more million dollars), changing the way the network operates.

The Netherlands model works due to high population density and took over a decade to change. The costs of operation are likely to be 5-10 times what we currently charge our ratepayers for water. Napier residents currently pay around $240 per household annually for unlimited water supply. Changing the network would likely increase the ongoing costs per household to over $1,200 per year. There would also be a large cost initially to rebuild the network and rough costs indicate that this could increase rates by around 20% annually for a ten-year period. This is likely to be uneconomic for our community.

There would still be chlorination in the network during contamination events and there would be boil water notices during these events.

We have put more money into water supply.

In the first three years of the current Long Term Plan, we are spending about $250,000 per year. From year 2021/22, we will be increasing our spending on pipe replacements and over next 30 years we have planned to spend over $30m for pipe replacement. These costs exclude the larger capital spend that is planned for new water related projects.

Major projects take resources and planning and take time to implement. We have brought a number of significant projects forward and our ability to deliver this accelerated programme will have its challenges.

We are going to accelerate our pipe cleaning programme. This progamme will be implemented during the winter periods when the water demand is low. We are also planning to change the way our water supply is operating by introducing new water bores and making changes to the pipe network. These are major projects and will help to reduce the water clarity issues. These projects might take at least three years to complete. With these works, we will experience gradual improvements of our water clarity issue.

 

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.

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.

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.

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 dirty tap water some households have been experiencing has higher levels of manganese and should not be drunk. 

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.

Our water source, the Heretaunga Aquifer, has naturally occurring manganese - one of the most abundant metals in the earth's crust. When water with manganese water with oxygen or chlorine, the manganese oxidises to manganese dioxide, a black solid that can be deposited in our 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.

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:

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 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.

The first dechlorinated water station, is located at Anderson Park (141 York Ave). The water station has four taps and users aren't charged anything.

A second dechlorinated water station located close to the city centre is being worked on.

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