Two failures of Heatra Undersink Water Heaters

26 Feb 2005
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United Kingdom
Just had my second Heatrae under-sink 10L water heater split wide open - I put the first down to possibly a bad batch, as they replaced it for me. The second one having failed in the same way leads me to suspect

a)the manufacturing defect is present in the replacement unit or
b)the issue lies elsewhere, possibly with installation.

I can't really see how installation can go wrong, with the pressure restricter in place as instructed and with Heatrae's own vented tap in use.....

So my questions are: has anyone else had an issue with Heatrae's heaters and b) who's heaters do I turn to next?!
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Are you sure you have the connections to the tap right,
why would it split if there was no pressure build up???
I think you will find the fault is with the plumbing. I have fitted loads, and unvented with the right kit, and never had a problem.
Interesting reading - would it have worked at all if in and out were reversed?!
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Well both units worked fine for 4 weeks, then....bang.

That's what I meant by "would it have worked at all....."

Anyway I have just checked yet again and the connections are fine.

Have another unit now by a different manufacturer. we shall see.....
Well both units worked fine for 4 weeks, then....bang.

That's what I meant by "would it have worked at all....."

If they'd split parallel to the cylinder axis, that would normally indicate that the cylinder had been over-pressurized. If I recall the details correctly, it should be impossible to over-pressurize the cylinder because the outlet is an open pipe. The tap drips as the water heats up and expands and this is often mistaken for a fault. Any obstruction in the outlet, or fitting a different tap, would split it very quickly.
heatrae's own vented tap used. maybe a fault on that, although it did drip as advised as the water heated. As I say, all seemed fine for a few weeks...
The new unit has one of these to connect to the mains cold in:

The diameter of the threaded part appears to be 16mm. What do I need to connect this onto the 15mm pipe that comes from the mains? Thanks.

Apologies if this is a bit cheeky asking here, but out of interest, are these under-sink units domestic use, and if you only need 2 taps (kitchen and bathroom) are they a better bet than replacing the tank with a multi-point boiler? I currently have a janus circulator on a Johnson and Starley warm air system, which I find a pain to use and want an effective way to replace it. I've not known of these things before, hence my curiosity!


Dan T

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