Some drinking water in Christchurch, Lyttelton and Akaroa is supplied through older lead-jointed cast iron pipes.
The public water supply networks in the Christchurch district contain 170.9 km of cast iron pipes (4.9% of the reticulation networks). 47.3 km (28%) of these were installed during or prior to 1940 and are assumed to contain lead joints.
Lead may leach from these joints when there is prolonged contact between the drinking water and the lead joint at times of no or little water turnover.
The Council started lead sampling in Christchurch, Lyttelton and Akaroa in September 2019. Initially only manual spot samples were taken but in 2020 the sampling method was changed to automatic sampling machines that take 24 samples over a 24-hour period. This method provides a better picture of exposure patterns.
Have you found lead in the drinking water?
Out of over 573 water samples taken in since September 2019, eleven samples exceeded the Ministry of Health's maximum acceptable value (MAV) for lead. The MAV is a health limit based on the maximum amount of lead considered safe for a bottle-fed baby to consume each day. It is based on babies' consumption because they are considered to be the most sensitive population group.
What is the public health assessment of lead in the drinking water?
We notified the Canterbury Medical Officer of Health, Dr Alistair Humphrey, about the results of our lead-sampling programme carried out in September and October 2019. He advised that the public health risk was extremely low and close to nil.
If you are concerned, you can contact your GP for professional medical advice.
We are required to notify our Drinking Water Assessor of all MAV exceedances and our planned corrective actions to manage the risk. To date these actions were considered to be acceptable in regards to the management of the event. The Drinking Water Assessor is also required to inform the Ministry of Health of such MAV exceedances.
When was it discovered that lead had exceeded the health limit?
The risk of lead in the water from lead-jointed pipes was first identified as part of our water safety plan reviews and risk assessments which commenced in 2019 under the Ministry of Health's new water safety plan framework .
Is it still safe to drink water from the tap if it's supplied through lead-jointed pipes?
According to WHO information (https://www.who.int/ipcs/features/lead..pdf?ua=1(external link), https://www.who.int/water_sanitation_health/dwq/chemicals/lead.pdf(external link)) lead is classified as a chronic or cumulative toxin. Chronic exposure is defined as continuous or repeated contact with a toxic substance over a long period of time (months or years). Our sampling undertaken to date suggests that there is no chronic exposure to potentially harmful concentrations of lead.
Traces of copper and lead can accumulate in drinking water that has been sitting for a long period in contact with metal plumbing fittings. Although the health risk is small, the Ministry of Health recommends you run your tap for a few seconds each morning, or after a long absence from your property, before drinking or washing dishes. This is to remove any metals that may have dissolved from your private plumbing fittings. For the purpose of water conservation, it's suggested you use this water for watering plants.
This simple precaution is recommended for all households in New Zealand, including those on public and private water supplies in the Christchurch and Banks Peninsula area.
What is the Council doing right now about its lead-jointed pipes?
We are reducing the use of lead-jointed pipes in the network, including taking some out of service and temporarily re-routing water through lead-free pipes. We are also continuing to take water samples so we can understand the extent of the issue and whether there are any changes over time. In the medium term, we will also speed up the replacement of lead-jointed pipes through our pipe renewals programme.
Is chlorine treatment of the water causing the lead joints to dissolve?
We can't say for certain whether chlorine treatment is a contributing factor to lead in the water.
Why do we still have old and damaged pipes supplying drinking water in Christchurch?
The Canterbury earthquakes caused significant and widespread damage to our drinking water supply network. We are working hard to prioritise and catch up on repairs and renewals for our underground pipes and other water supply infrastructure. The task is massive and complex, requiring significant time and investment. As we work, we are also bringing the network up to new, best-practice standards to make sure it is resilient and ready for the future.