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Dirty water – and how you can get it sorted

Some of our residents, particularly in Onekawa, Tamatea, Greenmeadows and Pirimai have experienced dirty water issues over the past year. We understand it is aesthetically unpleasant - and we're committed to fixing the problem. In the meantime, here is what you can do if you experience dirty water - and what we're able to do to fix it.

What you can do if you have dirty water

Turn on your garden tap and run it hard until the water becomes clear. If it is not running clear within 10 to 15 minutes, call our 24/7 Customer Service number (0800 462 7437). We'll arrange for a crew to come around and flush the mains pipes in your street. To help conserve water, please don't let your tap run longer than 15 minutes. Just call us if it the water isn't clear after this time.  If you can resolve the problem yourself by running the tap, we'd really appreciate it if you could still give us a heads up that you've had problems. It only takes a couple of minutes to complete the Report It form and it'll help us track issues and trends within our network.

Dirty laundry

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 taps 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. 

Not nice - but not unsafe

We regularly test the samples of dirty water to understand any potential health implications. Analysis of these tests show that there are elevated levels of manganese in the dirty water as a result of cleaning the pipe network and stirring up sediment. To have any health effects from drinking this water, you would need to ingest it frequently over a long period of time. Our recommendation is to avoid drinking dirty water and to flush the water until clear before drinking. Napier’s source water is naturally low in manganese ( less than  0.064 mg/L ) compared with the Maximum Acceptable Value of 0.400 mg/L. In December 2018, Dr Belinda Cridge from the University of Otago recommended a precautionary approach for vulnerable groups who may drink dirty water (including babies, pregnant women and the elderly). Dr Cridge concluded that “for most of the population the risk is very low”.

What is causing this dirty water

There are four major reasons why we've experienced dirty water in Napier water recently. They are:

  • Major work in pipework
  • Planned maintenance
  • Changes to the water flows within the pipe network.
  • Chemistry of our source water

Let's look at each of these in turn.

Major work in pipe network

From time to time, we carry out major repairs or replacement of pipes within our 481km-long network. When we do this, water within the network can get dirty.

Planned maintenance

Throughout the year, we carry our scheduled maintenance of the network. This includes pipe cleaning and flushing to remove sediments and other material which have built up inside  the pipe network. During and immediately after this maintenance work, some customers nearby the maintenance area can get dirty water through their taps. We advise customers that we think may be affected by leaflet drops - and also advertise more generally in local newspapers and through heavily-promoted posts on our Facebook page

Changes to the water flows within the pipe network

Sometimes, for operational reasons, we might change the flow rates and or even direction of water within the pipe network. This 'churn' can dislodge some of the biofilm that's built up inside the pipes and disturb sediments within the network.

Chemistry of our source water

Chemistry of our source water – We have lovely water from our Aquifer which is rich in dissolved gasses and minerals, including iron and manganese. Iron and manganese can cause colour issues in water supplies and as there is manganese present in the biofilm this contributes to the colour of the water when biofilm is dislodged.

What NCC is doing to sort this out

Short term: We're midway through our winter mains cleaning programme. Most years we aim to clean 100km of our network: we're cleaning 150km in 2019.

Longer term: We've brought forward several water infrastructure projects. We're spending more than $30m over the next four years, including more than $9m in 2019/20.

6 December 2019

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