Shower Water Temperature Fluctuating

23 Aug 2016
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United Kingdom
Hello Everyone,

We have a VictoriaPlum Aria square shower, fitted in January 2014, driven by a Worcester Bosch 24CDi combi-boiler. Everything has been good with the shower up until now and the boiler, here when we moved in 2004, has always worked well bar a new pump and has been serviced annually by Home Care.

About a month ago we noticed the temperature of the water from the shower was fluctuating, from perhaps a little too warm to cold enough to not want to stand under it. But this passes quickly and gets warmer again, then the cycle restarts.

So we called Home Care and the engineer cleaned out the heat exchanger, but to little change when using the shower that evening. The 2nd engineer replaced the heat exchanger but again to little change. The 3rd engineer hooked up his diagnostic kit to the boiler and ran the hot tap in the kitchen sink and all seemed well, ran the bathroom sink hot top and all seemed well. However when running the shower, the boiler would cut out after a few minutes where the shower would go cold and start up again where the water would get hot. So the engineer's view was that the shower was the issue and not the boiler.

So after some googling I found out that the shower was thermostatic and a change of cartridge could be the issue. So I fitted a new one of the same model and ... no difference.

So any thoughts would be appreciated, either from a plumber or gas boiler engineer, on what the issue could be. My research suggest the diaphragm in the boiler could require replacing, but persuading Home Care that's the case could be tricky.

Thank you for reading and sorry this post wasn't short.


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