Water tap mixer and shower

Hi Emanuel In response to your question, I think you have 2 separate problems. Firstly the mixer taps to the bath. If the hot and cold are on different taps and you are having issues with the flow on your cold water. You have one of two problems. If could be a fault of the tap itself not opening up fully and therefore not allowing the cold water through. Alternatively if is an issue with the pipe not allowing enough cold water through to the tap. This could be something as a ballfix valve on the pipe before the tap as if this isn't opened up fully if will restrict the flow to the tap. It would be worth checking to see if you have this valve on the pipe before the tap. It has a simple slot that you can put a flat headed screwdriver in and open it up fully. Second issue is with the shower and this will be due to you having an issue with the mixing valve within the shower controls. These can sometime be ordered and replaced. Alternatively you may have to replace the thermostat if this cannot be changed.

this is more likely to be a differential pressure problem, where does your hot water come from ?,combi boiler or hot water cylinder ? we need more information to be able to answer your question.

You didn’t say if the flow rates for each appliance had been checked before installation or if you have always had this problem or if it’s a new problem, if all these checks had been done prior to installation of each outlet and all worked correctly and this problem is new then I would try changing the thermostatic valves, hard one to diagnose without on site investigation

Hi the bath cold water may be gravity fed from tank in loft, also if its got flexi tap connections that have bends or kinks then this is also most likely causing an issue