Shower mixer problem

[Soumen]

Hello all,

I need advice on a bath tap/shower mixer unit. I have recently moved into a flat where the bathroom comes with a tap/shower mixer unit which has a "diverter" consisting of a button which you pull up to divert the water up through a flexible 'metal' pipe and the attached shower head instead of through the bath taps. When the button is down, both hot and cold water can be regulated through the spout, and the water pressure and temperature changes proportionately to the amount which either the hot or cold water tap is turned. So with both hot and cold on full, the flow is very good and the temperature is luke warm to cool - this is all fine.
The problem occurs the moment I pull up the diverter to switch on the shower. The water flow seems to reduce and the shower water temperature rises. I then tried just using hot water through the shower and that works fine (good pressure) - but the moment I switch on the cold water tap - the shower pressure decreases significantly but the temperature of the water seems to remain just as hot. So basically while the hot water is running via the diverter through the shower, upon also switching on the cold water creates only a reduction of shower water pressure but the water temperature remain just as hot.
Can someone please help diagnose the problem and recommend a solution?

Thanks,

Soumen

 

[Phil]

Not really sure what the problem is.

I take it you have a combi boiler?

If so it is normal for the hot flow to decrease slightly when the cold tap is turned on.

 

[Soumen]

Sorry Phil and thanks for your prompt reply. The problem is that with the diverter on and hot water only on, the moment I switch on the cold water, the water pressure drops about 50%, (instead of increasing due to the new flow of cold water), but the water remains hot (so the cold water does not seem to come through). For reference, if the diverter was off (i.e water through the spout), then there is no problem. And, 'yes', there is a combi-boiler but the problem I described above only occurs for the shower (not the tub spout or sinks).