DHW hot and then warm..and so on

[goofy gorilla]

hi guys - Just had a vaillant 831 combi boiler fitted about two weeks ago, working fine, i have set the DHW at 40 degrees....now when im running the hot tap, the water is hot it then suddenly goes luke warm, then back to hot again...and so on...whats happened ?....is this related to the faulty street stopcock that i have reprted to severn trent in my other thread ?...

 

[45yearsagasman]

A new stopcock shouldn't be the problem, but a contaminated plate heat exchanger is a possibility. As its new get it checked out as the work in the street may have caused a problem.