There's been a sudden spike in hot water cylinder failures across Christchurch and many in the industry believe it could be linked to chlorine in the city's water supply.
Plumbers, hot water cylinder manufacturers and property investors have reported a significant increase in broken cylinders in the past few months.
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Christchurch plumber Darren Chatwin says July and August have been the busiest months for cylinder repair and maintenance since the Canterbury earthquakes in 2010 and 2011.
"Our workload regarding hot water cylinders has probably gone up 400 percent," he says.
"I think some more investigation needs to happen with the council and with the hot water cylinder manufacturers."
Christchurch hot water cylinder manufacturer Superheat have had to double their production over the last five weeks, bringing in extra staff and working overtime to keep up with demand.
Managing director Trevor Edwards says it's "plausible" that chlorine, which was introduced into the water supply temporarily in March this year, is behind the sudden change.
"It's unprecedented, other than the earthquakes, that we'd have such a failure rate of hot water cylinders so it's an open question," he says.
"A protective layer forms on copper, and if that is eliminated by some other substance, that can cause corrosion."
Perhaps the most alarming element is that many of the broken cylinders are only a few years old. The stock in Christchurch is fairly new, as many were replaced following the earthquakes.
Property investor Tony Brazier is one of those feeling the hit - new cylinders can cost as much as $2000.
"The unusual thing about property managed is we get to see patterns, because there's a lot of properties doing the same thing, and we've had 25 cylinders go in a couple of months," he says.
"In fact in one case, we've had four cylinders go in a block of five in one month."
The Christchurch City Council was unavailable for comment.