Sols

Yes correct - apologies on terminology I've just moved in recently and started the changes in the house. I suspect the shower has been in there since day 1 so close to 20 years ago. Will look at replacing the shower for something that is suitable for a vented system, will hopefully report good news in due course. Thanks for all the help so far!

It was a combi boiler so heated the rads and hot water cylinder The gas boiler was maintained at a medium to high heat setting. I couldn't be more precise but during the cold spell the rads would have been piping hot along with the cylinder and the shower didn't have the same issues at that time. Yes it's an unvented cylinder image below. What would be the recommendation? A new shower unit as a result?

Hi - We installed a heat pump to replace a gas boiler about 5 weeks ago. Since then every time I have an issue where when I turn on my shower the water will come out cold/lukewarm for about 30 seconds, then the water will stutter and the shower will screech as it juggles the hot water until it is then sufficiently hot. It's as if once the hot water hits the shower unit all hell breaks loose until its at the correct output. Separately a new issue in the last week since adjusting the flow rate (as we could hear swooshing in some rads which might not be related to this issue at all) I now randomly have no water coming through the shower at all. If I power it off for a few mins and try again it will then work. The plumber has checked for any air pockets, has checked the filter in the shower unit and also adjusted the flow. We have the 8.5Kw heatpump 180L cylinder set at 48 degrees. I have a Mira Event XS Thermostatic power shower. Any suggestions on what to check are welcome.