The drinking water that comes from the Dunedin network supply is safe. However, metals such as lead can leach from pipes and fittings, such as taps, into the water if it’s been sitting for a while, such as overnight.
The amount of local lead leaching depends on several factors, including how corrosive the water is, what the pipes or fittings are made from and the amount of time the water is in contact with the pipe or fittings.
The Ministry of Health notes that taps are the main source of heavy metals found in drinking water in most houses, and advises flushing a small volume of water – about 500ml – from the cold tap before you use water for drinking, cooking or brushing your teeth. You should also run a cold tap for about 30 seconds each morning, to flush out the water sitting in your pipes overnight.
This flushing should reduce the risk of drinking water containing metals.
This is all that most people need to do, but longer flushing is advised in a few situations. Here are some examples where you need to flush your taps for at least two minutes and potentially longer.
- Your building has large diameter pipes, e.g. a factory.
- Your building is located a long way from the road, meaning more pipework where the water can sit (buildings 20-50m from the boundary – one minute should suffice, buildings 50-100m from the boundary – two minutes).
- The property has a complex water system, e.g. header tanks or irrigation systems.
- If the water has been standing for a long time e.g. holiday homes where water may not have been used for days or weeks on end.
To work through what’s required specifically for your site, you can get a plumber to check the materials and condition of the water pipes and connections on your property. There is also the option of installing a water filter to remove any lead coming into your home or business. For best results, we recommend a filter of less than 0.01 µm pore size.
You can also have your water tested by sending a sample to an accredited laboratory. A sample taken first thing in the morning before flushing your tap will show what’s in the water that’s been sitting overnight. If you flush the tap first, the water should be more representative of the water you are using most of the time.
If you have any health concerns you should contact your health professional.