Hastings considers independent investigation into cause of water cylinder failures

Hastings District Council has determined chlorination and high water pressure are unlikely to be the cause and is getting advice on whether to commit to an independent investigation. Photo / NZME

The pressure is on to find a solution to Hastings' mysterious hot water cylinder failures, with an independent investigation now being considered.

Hastings District Council has so far determined that chlorination and high water pressure are unlikely to be the cause of the widespread failures, and says an answer and viable solution to the issue may never be found, despite best efforts.

Statistics show low-pressure copper hot water cylinders (LPCU) are about 20 times more likely to fail in Hastings than in the rest of New Zealand.

An area covering Flaxmere, Saint Leonards, Mahora, Raureka, Mahora, Camberley, Tomoana, Longlands, Frimley, Woolwich, Parkvale, Akina and Mayfair has been responsible for 34 per cent of nationwide failures and warranty claims in the past 12 months.

Sales of replacement cylinders in those areas have more than trebled since the 2016 Havelock North water crisis, which had chlorine added to the city's water.

Warranty claims have also increased a similar amount in the same period.

Craig Thew, group manager asset management, earlier pointed out most New Zealand municipal supplies include chlorine, and other areas have not seen hot water cylinder issues to this extent.

Hastings does not have significantly higher dosages of chlorine than the rest of New Zealand.

According to Hastings District Council data across 40 sampling sites from June, the level of chlorination in Hastings where the cylinder failures are prevalent averages 0.5 to 1mg/litre.

Places like Christchurch typically range from between 0.2 to 1.0 mg/litre across their municipal supply, according to information on the Christchurch City Council website.

Taumata Arowai drinking water standards have a maximum allowable dosage of 5mg/litre and the level of chlorine residual cannot drop below 0.2mg/litre.

Another theory that has been posited by many has been changes in water pressure. Thew said water pressure for its supplies varies across the district, but did not play any role in the failure of LPCU.

"This is because they are low-pressure cylinders and they act to regulate the pressure of the water within them," Thew said.

Thew earlier highlighted that groundwater was naturally more corrosive than surface water takes, and he reiterated it could play a role.

"Groundwater is naturally corrosive, the raw water across Hastings has not changed, so the key is trying to identify the micro changes that may be contributing to the issue of these cylinder types failing early."

Master Plumbers CEO Greg Wallace last month called for an urgent independent investigation into the cause of the failures.

Thew said the council was considering this.

"We are getting independent advice, and this will help determine whether there's value in going to the potentially very costly expense of a detailed independent investigation, which may still not provide definitive answers or solutions," Thew said.

He said the council's advice to consumers still aligns with that of Master Plumbers - to not purchase low-pressure copper water cylinders in areas where the issue is occurring and instead opt for modern, robust cylinders made of stainless steel or vitreous enamel.