Hastings' hot water cylinder failures - the mystery continues six years on

Owner of Peak Plumbing & Gas Ltd, Grayson Allen, left, and apprentice plumber Michael Kaijser with a pair of wrecked copper hot water cylinders. Photo / Paul Taylor

Some may know that Hastings has been recognised as one of New Zealand's most beautiful cities, but lesser known is that the beautiful city is home to one of New Zealand's most perplexing plumbing mysteries.

In 2016, corrosion from chlorine was blamed for a spike in low pressure copper water heater (LPCU) failures as chlorination started following the water contamination event in Havelock North.

Master Plumbers CEO Greg Wallace said similar trends were observed in other places where chlorination was implemented, such as Christchurch, but while they have stabilised to average levels, Hastings has remained the worst place in New Zealand to have a LPCU.

He said they have determined two specific postcodes centred on Hastings city, 4120 and 4122, that are the problem areas.

"In Napier and Havelock North, outside those postcodes, we're not having any of the failure rates we've seen in those postcode areas."

The affected areas include Flaxmere, Saint Leonards, Mahora, Raureka, Mahora, Camberley, Tomoana, Longlands, Frimley, Woolwich, Parkvale, Akina and Mayfair.

Master Plumbers CEO Greg Wallace has sent out advice to all plumbers not to reinstall LPCUs in Hastings and thinks the local council should inform ratepayers of the issue too. Photo / Supplied

Wallace said data showed sales of replacement cylinders in those areas have more than tripled since 2016 and warranty claims have increased a similar amount in the same time period, both peaking in 2021.

According to 2018 census data, the entire Hastings District makes up about 1.7 per cent of occupied private dwellings in New Zealand, but Wallace said the failures in Hastings alone account for 30 per cent of LPCU failures nationwide.

"We think it's completely unfair on consumers that currently the failure rates are at this level."

He said analysis by both the Hastings District Council and manufacturers had been unable to produce a conclusive explanation for the localised rate of failures.

LPCU failures caused from chlorine typically happen by corrosion "pitting" at the base of the cylinder, however cylinders from Hastings which have been analysed showed inexplicably random corrosion points in the cylinder walls.

"There is no consistency in where the issue is occurring, so that again points to it not being a cylinder fault."

He said manufacturers and Master Plumbers have told all plumbers and suppliers not to reinstall copper cylinders in those two postcodes, and they were advising consumers too.

"We have never before to my knowledge recommended to not install copper cylinders."

He said the council approved of that action, but he thinks they should be more proactive with informing ratepayers of the issue too.

"Why aren't they communicating with their ratepayers about this? They're putting all this on plumbers."

Owner of Havelock North-based Peak Plumbing & Gas Ltd, Grayson Allen, said he and his colleagues didn't want to recommend or install something that was going to fail the customer.

"There were always failures in copper cylinders, but that was over time and generally that occurred with a higher spike in winter with frost but now we are seeing under 2-year-old cylinders, even less sometimes, put back into a house that are failing."

He said the only alternative at this point was to put in the more costly vitreous enamel or stainless steel cylinders which could sometimes cost clients over $1300 more than a LPCU.

Council group manager asset management Craig Thew said the council had ongoing investigations into the issue in collaboration with Master Plumbers and manufacturers since meetings with the industry last year.

He said low alkalinity water and different pH levels are potential contributing factors that led to the early failure of LPCUs.

"We do know that groundwater is naturally more corrosive than surface water takes, and the investigations to date have highlighted that the reaction appears to be related to certain groundwater sources more than others."

He said LPCUs are also known to be less resilient than more modern cylinders such as vitreous enamel cylinders.

He said Hastings' drinking water is monitored a range of ways to ensure it met New Zealand's health and safety standards, including the chlorine levels.

"The finding that this issue is largely limited to these two postcode areas within Hastings, when the whole water network is treated, indicates chlorine is not a primary factor."

He said the council was reviewing the drinking water testing interval to provide additional information to both further trace the potential causes to see if they could safely mitigate them and to provide more information to plumbers.

He said the council will continue to work with Master Plumbers and suppliers, but the effect of any changes trialled might not be felt for a number of years.