s53

Hi, I hope you can provide some advice on an issue I'm having with my Vaillant Ecomax 835e. When I turn on DHW downstairs, the boiler fires and provides hot water as expected. But upstairs when the shower or bathtub are used, the water will get (very) hot, then steadly decrease in temperature...

My boiler is 11 years old (the system was power flushed then). Just recently the hot water started to cut out. I contacted Vaillant who offered a £300 fixed repair contract. I have had two visits. On the second visit the diverter valve and plate heat exchanger were replaced. The first visit the...