Shower cold water issue

[Sergey P]

Hi,

I've got a cold water tank installed in the loft and hot water via combi boiler from mains.

The problem is that when I'm using shower it's always just hot water coming from it.
You need to turn the hot valve on very little to get any warm water from the shower, otherwise it seems like the hot water just doesn't let the cold water to mix at all.

It's a bit strange since the shower is located downstairs, so the cold water pressure is quite good.
For example if I use just the tap or unscrew the shower hose and check the water, I can see that the cold water flow is very strong, far stronger than the hot water.

Is there anything special about the shower in this case? Maybe the boiler detects it somehow and raises the pressure which doesn't let the cold water to go?
I'd really like to understand what's going on.

What would you do to fix it?

 

[Newboy]

How is your hot water supplied - combi, unvented cylinder, vented cylinder?

 

[Sergey P]

hot water - combi boiler.
cold water - loft water tank

 

[Newboy]

The shower mixer almost certainly needs balanced (equal pressure) hot and cold. At the moment, the hot supply is overwhelming the cold supply.

The flow rate will be better from the cold supply but the pressure will be significantly lower.

The easiest solution would be to provide mains supply cold to your shower