Wetbacks wearing out

Taieri residents with fire-boosted hot water cylinders have been urged to check they can deal with the particular quality of the water supply, after several reports of stainless steel cylinders corroding prematurely.

The Dunedin City Council said it had recently received from plumbers five reports of corroded wetback boosted hot water cylinders in East Taieri and Mosgiel.

Council water production manager Gerard McCombie said the affected cylinders were typically boosted by wood or coal fires heating water to about 70degC to 80degC, for example, to power radiators around a house, compared with the more usual temperatures of 50degC to 55degC.

He said an initial review of data from the five Mosgiel water treatment plants indicated the water met New Zealand drinking water standards.

The treatment plants were upgraded several years ago specifically to reduce the corrosiveness of the water in relation to copper cylinders and piping and some components in the treatment plant - specifically the vortex accelerators, which spun the water to disperse corrosive carbon dioxide - were refurbished a few weeks ago.

Mr McCombie said it was possible the recently affected hot water cylinders might have quite specific water quality requirements, which might only be achieved through the installation of an additional on-site water treatment system.

Property owners planning the installation of a new stainless steel hot water cylinder to operate above ordinary household temperatures should check the manufacturer's water quality operating requirements against the water chemistry for the area.

Plumbers and manufacturers were investigating the recent failures, and would report to the council, he said.


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