Plumbosolvency
Most drinking water in Aotearoa New Zealand is plumbosolvent. This means the water can dissolve small amounts of metals it may encounter, such as lead and copper in your plumbing fittings (like pipes and taps). Drinking water with high levels of heavy metal is a health concern.
Drinking water suppliers have a duty to ensure that the water they supply to you complies with the Drinking Water Standards, which sets maximum levels for metals in water. However, drinking water suppliers are only responsible for drinking water quality up to the point of supply, which is normally the toby outside of your property.
There may be metals in the plumbing within your property such as in the taps or other fixtures, which can have an impact after the water has been supplied. Newer, better-quality fittings are likely to contain less harmful metals. We recommend:
- When you first turn on your tap in the morning, run your tap to fill a large cup of water.
- Tip the cup of water down the sink
- You should also do this at other times when your tap has not been used for a while, like when you come back from holiday.
This will help remove metals that might have been dissolved or absorbed from your plumbing fittings.
Flushing your drinking water taps is recommended for all households, whether on public or private water supplies.
Other places – including commercial businesses, community buildings, and schools – should also have systems in place to ensure that drinking water taps are regularly flushed, particularly after periods of not using them like after the weekend and school holidays.
How you can test for metals in your household drinking water
Anyone can contact a laboratory to arrange a test for metals or chemicals in their household drinking water.
You can use our accredited laboratory registeroutbound to find a lab in your area.
What you can expect
- The lab will supply sample bottles and advice on collecting a sample.
- When sampling for metals, particularly in plumbing systems, the sample volume needs to be kept small (about half a cup – 100–150 mL).
- Sample collection methods change slightly depending on what you're testing for.
- To find out more about the effect that a specific tap has on the water coming out of it, a small volume of water can be tested. This sample would need to be a sample of the first water coming out of the tap (after water has sat in it for a few hours).
- If you want information on water quality in your household plumbing generally, rather than an individual tap, you'll need to flush the tap for a short time to avoid misleading results.
- If in doubt, ask the lab and follow their instructions for whichever type of test you are interested in.
Getting test results
- It usually takes several days to get a result. The lab will generally send a written test report back and potentially call the resident to discuss the results, depending on the results and the lab.
- A lab can only give generic advice regarding the results. Any follow-up actions would sit with you (for example contacting a plumber for new plumbing fittings).
How drinking water suppliers test for metals in supplies that they manage
Water suppliers should use flushed samples of water for routine metal testing.
In ordinary language, flushing means letting the tap run for several minutes before taking a sample.
New Zealand's Drinking Water Quality Assurance Rules (the Rules) apply here. These Rules say all water samples that require laboratory analysis must be collected according to instructions and specifications provided by the laboratory.
Laboratories require pre-flushing when testing water quality in the water supply network (rather than private fittings).