Have you found lead in the drinking water?
During 2021 we continued our sampling programme using automatic samplers over a 24-hour period (samples collected every hour over 24 hours). The samples were collected from private properties that are connected to old cast iron pipes.
|
Sampling sites and process |
Pre-1940 cast iron pipes – Christchurch |
Pre-1940 cast iron pipes – Lyttelton |
1940-1950 cast iron pipes |
Total |
|
Sampling sites |
120 |
12 |
23 |
155 |
|
Sample process in lab |
2832 |
288 |
552 |
3672 |
Out of the 3672 samples taken only three samples exceeds the MAV. These three samples were early during the programme and were on each occasion the first sample out of 24 taken. After changing the flushing time from 2 mins to 10 mins no further MAV exceedances occurred.
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 drinking water?
Initially in 2019 when our spot sampling targeting prolonged contact between pipe and water found some MAV exceedances, we notified the Canterbury Medical Officer of Health, Dr Alistair Humphrey, about these results. 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 had also notified the drinking water assessor of the previous results. We are required to notify the new regulator Taumata Arowai of all MAV exceedances for any determinand listed in the Drinking Water Standards and our planned corrective actions to manage the risk.
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, 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.