An independent investigation by Stantec Consulting has found the cause of Hastings' alarmingly high hot-water cylinder failures. Photo / Paul Taylor
An independent investigation by Stantec Consulting has found the cause of Hastings' alarmingly high hot-water cylinder failures. Photo / Paul Taylor
A new report has solved the mystery of why Hastings hot-water cylinders are failing at alarmingly high rates, and offered a potential chemical solution.
Postcodes 4120 and 4122 (which represent most of Hastings’ urban area) were responsible for 34 per cent of nationwide failures and warranty claims over one 12-month period last year.
Two of New Zealand’s largest hot-water cylinder manufacturers excluded Hastings from warranties for their LPCUs last year, citing “localised water conditions”.
An independent investigation from Stantec Consulting, commissioned by the council and released to Hawke’s Bay Today this week, identified that chlorination was “very likely an important compounding factor” in the copper pitting seen on the cylinders.
But the report found that the reason Hastings is having higher failure rates than other areas of New Zealand with chlorinated water, was that water from the Frimley and Wilson bores in Hastings had lower alkalinity and low dissolved organic carbon characteristics, which are associated with a propensity for copper pitting.
The report recommended that Hastings District Council add phosphoric acid or sodium silicate to the water supply, each of which work in different ways to prevent rapid copper corrosion.
The alternative is removing copper elements from the water system, which would mean homeowners would likely bear the majority of the cost to address the issue.
Removing chlorine from the equation is not a possibility for the council as its addition is required by New Zealand’s drinking water regulator, Taumata Arowai.
“Removing it is not an option as the safety of drinking water takes precedence,” a council spokesperson said in a statement.
Teresa Nicol, one of those affected by hot-water cylinder failures in Hastings, says the council should take financial responsibility for those affected. Photo / Paul Taylor
The Stantec investigation said phosphoric acid or sodium silicate were both “found in many food and beverage products” and when added to the water supply, they could help form a protective coating on the surface of copper components in the water network.
Phosphates are commonly used in corrosion control for water across Australia, the UK, the US and Canada.
The benefit is that it would protect the entire system equitably within a few months once the protective coating had formed, the report said.
A non-treatment approach would mean there would need to be a gradual replacement of copper-based plumbing and hot-water cylinder components in the water system with non-copper components.
The key challenge with this approach, identified in the report, is that it is largely dependent on homeowners and could take a long time.
The report states that the chemical approach would be Stantec’s recommended option, as it gives the most equitable means of copper pitting mitigation for Hastings residents.
“I say the council is responsible to help financially pay for those of us who have been affected, no matter what their solution is,” Nicol said.
She said she would be open to adding phosphoric acid or sodium silicate to the water, but only if the council could guarantee that would stop the corrosion before they did it.
He said the council should investigate how many cylinders had been replaced in the system, and how many copper cylinders were damaged already, before deciding whether to add another chemical to the water.
“It depends on how much is going to add to people’s rates as well.”
He was not looking for reimbursement, but he said he would like the council to officially admit chlorine was one of the causes of the failures.
A council spokesperson said in a statement that staff would go through the information, recommendations of the report and other expert advice before discussing the next steps in council meetings.
“As expected, the report points out that this type of pitting is ‘notoriously complex and is still not well understood’,” the spokesperson said.
“It also notes that it is highly unlikely that the issue can be fully remediated, as the type of cylinders used and the way they are used, can contribute to the issue.”
The statement said the council and the community would need to weigh up the cost, likelihood of success and implications of each option.
“While any option selected will be within the parameters of providing safe water for drinking, options can have other impacts on wider water users and potentially on the environment.”
The spokesperson said council advice at this stage was still for residents to use more durable non-copper cylinders.
James Pocock joined Hawke’s Bay Today in 2021 and writes breaking news and features, with a focus on environment, local government and post-cyclone issues in the region. He has a keen interest in finding the bigger picture in research and making it more accessible to audiences. He lives in Napier. james.pocock@nzme.co.nz
