Council accepts chlorine damaged cylinders, rules out compo
The Christchurch City Council has accepted chlorine in the public water supply is to blame for thousands of hot water cylinders failing, but has ruled out compensating affected homeowners.
More than 2000 cylinders have been replaced since June and a University of Canterbury study concluded chlorination was the likely cause of corrosion – and that chlorine could cause further problems to copper pipes.
The investigation was commissioned by Woolston manufacturer Superheat and headed by Professor Milo Kral. Four defective cylinders were analysed, which were either 180 or 225 litre capacity and between three and 10 years old.
In his report, Kral said: ‘‘The pitting observed was most likely due to the presence of chlorine and was influenced by the presence of iron in the sediments that settled to the bottom of the cylinders.’’
Other factors may have also played a part, such as temperature, details of installation and other aspects of water chemistry, he said.
If pitting occurs, cylinders usually cannot be fixed and have to be replaced at a cost of about $2000. Even if chlorination treatment stopped, the damage may already be done, the report said.
Council water supply improvement programme manager Helen Beaumont told The Press columnist Mike Yardley the council had considered the report and the conclusions reached. It would not get it peer reviewed, as three waters manager John Mackie earlier suggested.
‘‘We agree that the presence of chlorine in the water, along with the other factors noted in the report (such as temperature, details of installation and water chemistry), has contributed to the observed pitting corrosion.’’
How’s your hot water cylinder? I’ve had to replace two at my place in the past 12 months, two seasoned veterans which finally fell prey to corrosion after 45 years of faithful service, since being installed when the house was built.
Did the chlorination of the Christchurch water supply expedite their termination? Possibly, but over four decades of continuity is a herculean performance. Today’s standard cylinders generally average about 15 years.
It’s been a month since the report was released following the investigation into the spike in failures of Christchurch copper hot water cylinders (HWCs). Cylinder manufacturer Superheat commissioned the probe led by Canterbury University’s Professor Milo Kral. Forty failed copper HWCs were inspected using an endoscope camera, all showing signs of pitting in the bottom dome. Some were only two years old. Four were selected for further testing, representing a range of ages, manufacturers and Christchurch locations.
The research found all the tested HWCs failed due to leaks caused by pitting corrosion, most likely due to the presence of chlorine and influenced by the presence of iron in sediments that settled to the bottom of the cylinders. Superheat managing director Trevor Edwards is adamant that ‘‘in the absence of a credible alternative proposition, the chlorination of the Christchurch water supply by the city council has caused the unprecedented failure of copper hot water cylinders’’.
You will recall that following the report’s release, city council Three Waters Manager John Mackie said the council would look to peer-review the research with the agreement of the researcher. And that’s the last we heard from him on that.
Now the city council’s Water Supply Improvement Programme Manager, Helen Beaumont, confirms the report won’t be peer-reviewed, telling me ‘‘we have now had the chance to consider the report and the conclusions reached. We agree that the presence of chlorine in the water, along with the other factors noted in the report (such as temperature, details of installation and water chemistry), has contributed to the observed pitting corrosion’’. She asserts there are multiple factors that can contribute to cylinders failing, including ‘‘the quality and thickness of copper used’’.
Edwards is incensed the council is partly apportioning blame to the manufacturers, saying Superheat, Rheem and Peter Cocks meet the New Zealand Standards, are regularly audited and ‘‘the thickness and quality of the copper is one of the items that is checked with the measurement’’.
Following chlorination in March, Superheat estimates Christchurch has experienced more than 2000 HWC failures above normal replacement patterns. Edwards says ‘‘failures are likely to continue even after chlorination stops as the pitting corrosion is irreversible’’. What can you do to safeguard your cylinder? Install a chlorine filter in the water supply line, or use stainless steel or glasslined HWCs.
Interestingly, the council has revealed on its website that pitting corrosion occurs more commonly in bore water (underground-sourced), due to its chemical composition. Unlike Auckland and Wellington, where rivers are sourced, Christchurch is similar to Napier and Hastings, where they also experienced a spike in HWC failures following chlorination.
At no stage did our council warn or consult the public about the adverse impacts on HWCs, when adding chlorine, nor the financial consequences. Law firms have been actively perusing Kral’s report. Beaumont reaffirms ‘‘the council will not be compensating property owners’’, due to ‘‘multiple influencing factors’’. But maybe this should be tested in court, or even the Disputes Tribunal.