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Drinking water and lead

Microbial Risk Assessment Of Land Use On Drinking Water Supplies
Microbial Risk Assessment Of Land Use On Drinking Water Supplies

ESR focuses on the impact of water contamination on communities and works to reduce the risk of contamination in the first place, by providing advice about drinking water infrastructure and management. We also support public health responses, such as when high lead levels were detected in Waikouaiti's drinking water supply in early 2021. ESR scientists contributed epidemiological, forensic, clinical, toxicological and risk management expertise as well as drinking-water knowledge to determine the potential risks from the water supply and to assist with the investigation into the cause of the lead.

This incident raised an issue that is relevant to the whole country, because lead pipes and fittings can be present in the infrastructure of homes and buildings without people knowing about them. If water sits in lead pipes for a while, the lead can begin to leach into the drinking water.

The easiest way to remove this lead from drinking water is to flush your taps if water has been sitting in the pipes for a while. For most people, that means running about a cup of water from your kitchen sink in the morning, before using water for drinking or cooking.

Former ESR Toxicologist Dr Belinda Cridge answers frequently asked questions about lead in drinking water below. 

Frequently asked questions about lead in drinking water

How does lead enter our drinking water?

Most people get their drinking water from the main water supply, which is a big pipe that runs down your street. Then each house has a pipe that draws off from that main pipe and brings the water to the pipes that run through your house. The plumbing within the main supply, the pipes in your house, and the sink fixtures can all contain lead. Most towns in New Zealand have drinking water that is slightly corrosive which means if water is sitting within those pipes for a while, it can accumulate some lead. More information on the drinking-water in your area, and whether it might be corrosive, can be found on your local council website.

So how do you remove lead in water?

It’s very simple—all you need to do is flush the water out of your tap if it’s been sitting for a while. For most people, that means flushing your tap when you first wake up to make sure you get rid of the water that has been sitting in the pipes, and then you will start to draw in fresh, clean water from the main supply on the street. It is the local council’s responsibility to make sure this water is lead free.

If you are planning a renovation, make sure you talk to your plumber or plumbing supplier to make sure that you are sourcing tapware that complies with the standards for lead. Some cheaper taps can still contain high levels of lead, as explained in this Master Plumbers report.

How much water do you have to flush out of the tap?

For most people, you need to flush a cup of water. There are certain populations like people who are pregnant, infants, or young children, who are more susceptible to lead. If your household has vulnerable people, you might flush two cups, rather than one, just for the peace of mind. And this is something you can involve your children in—show them how to flush the taps and talk to them about we get healthy water to drink.

If your connection to the street is miles away or if you are on a farm or lifestyle block, you might need to flush more than a cup. A good rule of thumb to use is that for every metre to the connection point, flush for one second. You can walk the distance from your house to your letterbox and estimate how many metres that is (e.g. if it’s about 20 metres down, then you should flush water through your tap for 20 seconds).

Do you need to flush all the taps in the house?

You should flush any taps that you will be drinking from or using to cook. For most people, this means you just need to flush the kitchen tap, but if you plan on drinking from another tap, you can flush it as well. You don’t need to worry too much about the water used for brushing your teeth, because it is such a small amount, but if you want to be safe, you can flush that water as well. You don’t need to be worried about the water you use for showering or bathing.

What can you do with the water you flush out?

You can use that to water plants, in your clothes washer, or put it in the cistern of your toilet. Avoid using it on food growing in your garden, but it’s safe to water your flowers with it.

Should I use cold or hot water?

You should use cold water to flush your taps. If you use hot water, it draws water from the hot water tank and won’t flush out all the pipes in your home.

Something else to be aware of is that boiling water can concentrate any lead that’s in it, so ideally you should not fill your kettle first thing in the morning. Something you can do to protect everyone in your house is to fill the kettle the night before, so it’s ready for the next day.

Is flushing the water once a day enough?

In most cases, you need to flush once in the morning and that’s good for the rest of the day. If you’ve been away all day for hours and haven’t used the water, you can flush it again for good measure. A good way to do that is washing your hands at the kitchen tap when you get home, before drinking or cooking.

Another time when you should to flush the taps is when you are returning to a home or building after being away for a while. For example, if you have a holiday home that’s been sitting empty for a while, you want to make sure to run the water in all the taps for a few seconds. The same is true of a school that’s been sitting empty over the school holidays. When you get back you want to make sure to run all the taps and drinking fountains.

What do you do if you’re on tank water?

Have a look at some of the guidance for people on home water systems because there's a few other things you need to be aware of. For those people on tank or their own supply, there's a lot more you should be aware of in terms of your health and safety.

When I do a web search there are lots of webpages from the U.S., is the information still okay?

Any information you find describing how lead leaches into water will be correct, but the rules about who is responsible for fixing the problem are a little different. The U.S. is currently undertaking a huge amount of work to replace lead ‘service lines’ in their drinking-water networks. The service line is a pipe that runs from the main water pipe in the street into your house, and in the U.S. many of these are known to contain lead. The U.S. government has decided to offer funding to help replace these lead service lines, but this support is not available in New Zealand. Here the home or property owner is responsible for maintaining or replacing the plumbing from the connection to the water main in the street. The drinking-water supplier (local council) must provide safe water to this connection, after that it is the responsibility of the property owner to ensure that the plumbing is safe.

What’s the main thing to remember?

Flush about a cup of water and you’ll draw in the freshwater from the main supply. That water is clean and safe to drink, so keep drinking it because it’s a very safe and healthy option.