We have a Mira mixer shower which worked with a condensing boiler and also had a pump fitted due to low water pressure. We had new Worcester Bosch 30i combi boiler fitted last week. Since then the shower comes on at normal pressure for 90 seconds then pressure drastically reduces - if we turn up heat pressure returns but after 90 seconds drops to practically nothing again. Installer saying must be shower fault but it was working fine before new boiler installed. Any ideas please?
So the shower was previously fed from a hot water cylinder. Was the cold to the shower also converted to mains pressure when the combi was installed?
Yes previously fed from hot water cylinder and cold water tank in loft. Presume it was set up to have cold from mains.
If the hot and cold pipes are out of balance it would cause issues with the shower. Need to try confirm if the shower cold is from the mains. Do the cold taps in the bathroom have more pressure than before the boiler change?
Yes the cold taps have more pressure than before. I’ve just turned shower down to coldest setting and there’s no water coming out so I think you’ve solved it - I don’t think they connected the cold to the shower to the mains!