Combination Boilers

I have recently bought a house with a new sealed combination boiler installed. All is well with the thing until we decided to have a thermostatic mixer shower installed in the bathroom upstairs. It has transpired that the cold water pressure isnt sufficient to open the non-return valve on the cold water side of the mixer, which means that the pressure is low and sometimes only dribbles out until the mixer is thumped. Taking out the non-return valve is an option but it does mean that there is a risk of the hot water feeding back into the cold water tank. The reason the cold water pressure is low is that it is still fed to the bathroom via a cold water tank in the attic. Logic dictates that with a sealed combi boiler the need for a water tank is done away with, however one still exsists! My question is, can I get rid of the water tank in the attic and feed the bathroom with the rising mains that feeds the tank?
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With a combi boiler the cold to the shower should be off the mains and the hot off the combi which is supplied from the same cold mains. Then equal high pressure on bothe hot and cold. No need for a non-return valve.

Just take the cold for the shower off the mains. Leave the tank if it is doing no harm and it will supply the toilets and other cold supplies.
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Yes, you can. The normal way is indeed to remove the cold water cistern as well. You should find that it all works fine after that.
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Chris French, Leeds

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You might find the cold was left on a tank supply cos the mains can't supply an adequate amount of water if more than one tap is turned on and the tank ball valve supply could be restricted to reduce its effects.
Rgds
Andy R
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