Hot water cylinders still failing in city

Hot water cylinders in Christchurch are still failing, two years after the city’s water was chlorinated.

Yet despite a city council admission that chlorination was one factor causing the failures, a case in the Disputes Tribunal found the council was not liable to pay for a replacement cylinder.

Failures were first reported in August 2018 and, later that year, a report commissioned by a hot water cylinder manufacturer determined chlorine was most likely to blame for the failures.

The manufacturer who commissioned the report, Trevor Edwards of Superheat in Woolston, estimated at the time there were 2000 failures citywide.

This week, he said the total number since 2018 would now be closer to 12,000.

Multiple plumbers said although failures were not happening as often as in 2018, there was still steady demand to replace cylinders.

Copper cylinders have failed since chlorination due to pitting, a form of corrosion which causes tiny holes in the cylinder. If pitting occurs, cylinders usually cannot be fixed and have to be replaced at a cost of about $2000.

Plumb Right owner Hamish McPherson said he was still replacing about one cylinder a week, compared to one a month before chlorination.

One client’s cylinder recently failed after just three years. He suspected it was due to chlorine.

McPherson recalled recently replacing a 10-month-old cylinder as well as two others which were just a year old.

‘‘Historically ... I’d be surprised if someone’s only lasted 10 years. Now I’m not surprised if it’s only lasting one year,’’ he said.

McPherson said he no longer installed copper hot water cylinders, instead opting for steel ones, which were more reliable.

Taylored Plumbing owner Andy Taylor said he replaced two cylinders on a recent week, one of which was installed in 2011. He suspected chlorine caused both to fail.

‘‘To me, it’s reasonably apparent that it is a cause, a fault, of the chlorination being introduced into the water supply.’’

Geoff, who asked for his last name not to be used, had a 20-year-old hot water cylinder fail in January this year in a rental property, which his plumber said was due to corrosion caused by chlorine.

‘‘I think there’s a fair case for those of us who had to replace cylinders to be compensated in some way by the council, because they’ve made a decision and it has brought a bad result,’’ Geoff said.

Christchurch City Council’s head of three waters and waste, Helen Beaumont, agreed chlorine, along with other factors, contributed to pitting corrosion in the cylinders.

She said the council would not compensate homeowners because failures were caused by multiple factors and chlorination was inevitable due to the council’s Health Act requirements.

Beaumont said a 2019 Disputes Tribunal ruling affirmed this position, though the council refused to release the ruling.

Christchurch residents have laid 248 complaints with the council about hot water cylinders since chlorine was added to the water.

University of Canterbury corrosion expert Professor Milo Kral, who was commissioned for the 2018 study into the failures, said removing chlorine from the water, anticipated for the end of the year, would not be an overnight fix.

Instead, he predicted there may be a shorter-than-normal lifespan for hot water cylinders in Christchurch.

‘‘Historically ... I’d be surprised if someone’s only lasted 10 years. Now I’m not surprised if it’s only lasting one year.’’

Hamish McPherson Plumb Right owner