Treated drinking water

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Ministry of Health advisory
Water issues
Plumbosolvent water
Water supply, wastewater services and stormwater

The Waikato District Council is responsible for ensuring that our water supplies comply with the Drinking Water Standards of New Zealand (DWSNZ 2005) revised (2008).

Waikato district's water comes from a variety of sources and so a range of water treatment processes are used at individual plants. Each treatment plant is designed to deal with the characteristics of the source of supply.

Ministry of Health advisory

The drinking water standards also require all councils to pass on a Ministry of Health advisory about flushing water pipes which haven't been used for more than half a day.

This is because water settles in household and other buildings' pipes overnight or during long gaps between tap use, along with any metal particles from the pipes themselves (called, 'plumbosolvency' - see below for more details).

That's why it's a good habit to get into to run the tap for a few seconds first before filling a cup, glass or other container with water for drinking or cooking food. 

The advisory states that "...although the health risk is small, the Ministry of Health recommends that you flush a mugful of water from the tap each morning before use to remove any metals that may have dissolved from the plumbing fittings...”.

Waikato District Council recommends this simple precaution for all households including those on public and private water supplies. 

Fluoridation

Fluoride is added to council water supplies in Huntly, Te Kauwhata, Pokeno, southern districts and Ngaruawahia. We are aiming to add it to water supplies in Tuakau later this year.  

Water issues

Problem: Yellow to rusty brown water, stains on washing or stale taste.                   
Cause:     Rusting iron pipes at home or sediment in the water supply.
Try:          Turn a cold tap on full for 20 minutes. If the water turns clear, the brown colour is probably due to rusting iron pipes at home.

If the water doesn't clear or it still tastes stale after turning the tap on full, the problem is not in your pipes. Small particles settle at some places in the water system. Dirty water results if this sediment is disturbed in some way. Contact us to request a flush of the supply mains - call our freephone 0800 492 452.

Problem:  Metallic taste or smell.
Cause:      Corroding pipes or fitting (plumbosolvency).

Plumbosolvency is when minute traces of the metals in your pipework and fittings leach into the water when it is not being used. As per the Ministry of Health advisory above, turn a tap on full for a couple of minutes to flush the pipework - particularly if it's being used for drinking or cooking. See below for more details on plumbosolvent water.

Problem:   Green or blue water, green stains on plumbing.
Cause:       Corroding copper pipes at home.

Problem:   White, cloudy or milky water.
Cause:       Air in the water.        

If you hold up a glass up to the light, there will be tiny bubbles moving up from the bottom of the glass. This is not harmful. We can flush the mains to get rid of the air if the problem continues - call us on our freephone 0800 452 492 to discuss this if you need to.

In some case, calcium has been known to leach from cement-lined pipes. This often improves with time.

Problem:   Slight smell of chlorine.
Cause:       Chlorine in the water. Council adds chlorine to disinfect the water. This is not harmful and the smell will not continue for long.

Plumbosolvent water

Plumbosolvent water is water that can dissolve metals in fixtures and fittings. If left undisturbed for several hours in a pipe or on a metal surface, the water will absorb small amounts of dissolved metals which can then be delivered via the tap to your glass, cup or kettle. The amount of metal which will dissolve from a fitting depends on how 'plumbosolvent' the water is; temperature; the composition of fittings used for the plumbing set up; and the length of contact time between the static water withing the pipe.

In New Zealand, the heavy metals that dissolve in drinking water from plumbing fittings are lead, nickel, cadmium, copper and antimony. 

All water is plumbosolvent to some extent, but soft, slightly acidic water dissolves metals most readily.

Water supply, wastewater services and stormwater

Water supply and wastewater are two infrastructure considerations you need to consider in relation to obtaining consents when developing land, building or renovating. Find out more in land and property - and see the water supply and wastewater forms below for more information on how to connect to a water supply or wastewater service.

Find out more about how your actions can impact on water supply, wastewater and stormwater. Read about how you can save water with Smart Water.

Related documents

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