Cylinder solution potential

Perhaps a majority of Cashmere homes have not encountered this water management difficulty, or there would be uproar. CCC rest on uncertain statistics and leave HWC faults to commerce to resolve.

So this page gathers clues available to residents on how to relieve the cylinder-element burnouts. Starting with the website author’s own experience:

25 years in Cashmere with water heated by the old-style, small corrugated-copper tank; the earthed, element connection wiring as revealed here:

Cashmere copper cylinder electronics 4Jan2016
Cashmere copper cylinder electronics 4Jan2016

– No problem ever, with tank insulation wrap the only modification in that period. On ripple-control, this cylinder is often switched off to conserve power and 30 minutes-on heats enough water for showering. Note earthquake damage to wall join.

Is the copper in the above system what stops any tank corrosion? Inspection invited. A slow build-up of hard white calcium flakes on the kettle element has been observed in the same house in recent years. This has put small floating flakes in the boiled water as a new inconvenience. Larger, beige deposit flakes sink in the kettle for emptying out. More resident comment on the chemical content of the water supply, and what to do about it, is made here:

Comparison of Cashmere Water Analysis Report with CCC average chemical analysis of Christchurch water identifies a much lower pH, 6.9 versus 7.8-8.2 with 71% higher Hardness and 54% higher Alkalinity values in Cashmere

Hill Labs finding: “slightly hard… The parameter pH did NOT meet the guidelines laid down in the publication ‘Drinking-water standards for New Zealand 2005 (revised 2008)’ published by the Ministry of Health for water which is suitable for drinking purposes.” Cashmere Water Analysis Report p.2.

Is this the precise problem here? … Is water-dosing involved? …

Chlorine was added to all Christchurch water supplies as a temporary safety measure after the Canterbury Earthquake disaster of February 2011 –

Chlorine in the water supply would have lowered the pH, increasing acidity, and could perhaps account for some of the tank corrosion experienced.

Ref. p.12, Determinand GV “pH 7.0–8.5 Should be between 7 and 8. Most waters with a low pH have a high plumbosolvency. Waters with a high pH: have a soapy taste and feel. A pH less than 8 is preferable for effective disinfection with chlorine” and p.150, “pH A measure of the concentration of hydrogen ions in water. It is the negative logarithm to base 10 of the concentration of H+ in the water. A low pH indicates an acidic water; a high pH shows the water is alkaline; a pH of 7 is neutral. The pH of water is particularly important in water treatment processes such as coagulation and disinfection.”


Peter Cocks Ltd has been bought out by Rheem, Auckland

– Rheem New Zealand announces acquisition of Peter Cocks, 15 October 2015

Commission clears Rheem to acquire Peter Cocks, 3 February 2016

+ see RinnaiService Centres – Canterbury.

N.B. Hot water heat pump solution – Coulter household to CRA 1.6.16

The combination of a titanium element and a sacrificial anode is deemed a successful fix –

N.B. An “industrial” grade element fixed the burnout problem after years of replacements for a Bowenvale committee member’s household, though this pre-dated the 2010-2011 earthquakes. However, the tap water is not trusted to drink from and they regularly source spring water for this.
Editor 7.7.17: I have never seen more lime slake buildup in one place than in this household kettle. And they have been stricken with serious kidney stone illness.

CRA suspects leached lime from new concrete in the lower Dyers’ Pass Rd reservoir is the root of this problem, which we must hope will diminish over time. But the supply side needs more research yet.

Refs. + + +
Impacts of Water Quality on Residential Water Heating Equipment – U.S. Department of Energy, November 2013 – Pacific Northwest National Laboratory