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Case Study:Stainless Steel Hot Water Cylinders

These problems will become more prominent

Stainless steel cylinderImage 1: Cylinder for replacement
Stainless steel cylinderImage 2: Cylinder with lagging removed
Stainless steel cylinderImage 3: Immersion heater

First picture shows existing cylinder for replacement-this is the following history related to this installation:

1) Stainless Steel Cylinder was installed three years ago

2) Cylinder is Direct so the main source of heating the water is by immersion heater

3) Has had three replacement immersion heater in the last three years

4) This cylinder has stared to leak and has damaged the ceiling below

I was called in to carry out the replacement for this customer but felt further investigation was required, just to warn other installers, electricians and DIY persons:

These cylinders are excellent valve and their installation is on the increase, but I believe these problems will become more prominent:

These are my findings:

1) Removed some of the foam lagging to reveal areas of corrosion

2) Area leaking around the immersion heater boss

3) To the area at the top of cylinder I have used a pressure test pump to raise the pressure to 0.5 bar - this showing in the video and photo water spraying out of the pinholes in the corrosion

4) The photo of the exiting immersion heater is that of the Incaloy type which is required for Stainless Steel cylinders

5) According to manufacture all immersions heaters to have 100% Incaloy or Titanium

6) We do not know the history of the previous two immersion heater and could assume they may have been made out of copper causing electrolytic corrosion

With this installation I believe there is another underlying problem, again these are my findings:

This property is 112 years old and still has the old galvanize water main pipework coming into the house

So this corrosion, what were the causes?

Where the other two immersion heaters standard copper type or faulty?


More likely the existing galvanize water main pipework causing electrolytic corrosion:

To sum up, the replacement cylinder is now a copper cylinder with a Anti Corrosive (Incaloy) Immersion Heater.

If any one has other issues about corrosion I would be pleased to here from them

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