We have a combi boiler fitted last August in Kitchen and have a cold water tank in the loft.
Water flow from all taps is reasonably good including the bath.
The bath tap is a mixer which has a knob to switch to shower so its probably not the best option on the market but what we had when we moved in last year.
When we move the knob to shower position the water is either boiling hot or freezing cold depending on how you have the taps opened.
I have noticed that when the cold tap is only open we have a good flow from shower, when the hot tap is opened the flow becomes very hot and pressure is at least half of just having cold tap open.
Also noticed that ater this happens the cold tap at the basin in the bathroom has a small amount of hot water.
Seems to me like the cold water pressure is not enough and the hot water from the combi is winning the battle of pressure and forcing its way down the cold water pipe.
What is my best option, i do not want to increase head height in water tank, its probably about 1.5 to 2 M above shower.
Bath has 22mm pipes and basin 15mm.
The flow from the mixer when switched to bath filling mode is OK and we can adjust the taps to get a nice warm mix of water.
Also it does seem that occasionally it has worked the shower but my wife thinks otheriwse.
Combi is a Main 24
Hope you can help?