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I've got a grohe mixer valve shower and no matter how far I turn the temperature dial towards cold ,the water coming from the shower head never gets properly cold,ie it never gets down to the temperature of the cold water feed,the coolest it will go is still pretty warm.
If I take the temperature knob off and turn the underlying brass knob further towards cold (IE past the limits that exist when the temperature knob is attached) then it will go colder, but then when I refit the temperature knob, I then can't get the shower hot enough.
Does this indicate an issue with the thermostatic valve cartridge,ie should I be able to get 100% cold water feed, or is it correct that there always a significant element of hot water being mixed in.
If it matters it's a grohe shower fitted in 2007,and the valve has not been replaced ever. The knobs turn smoothly and it doesn't drip or leak.
It might mean that the flow rate of the hot and the flow rate of the cold is not balanced.
Where does the hot come from, unpressurised cylinder? How is this filled? Header tank in loft?
Where does the cold come from? If this comes from the rising mains, then it will have more pressure/greater flow, than the hot in the unpressurised cylinder, hence the imbalance.
If this is the case then the cold should be replumbed to come from the header tank. ie. Both hot and cold at the same pressure.
Thanks for that,but I don't think it's due to different water pressure of hot and cold. The hot comes from an unvented presurised cylinder,and the cold is direct from the mains,so they should be similar in pressure.
If you are sure your hot and cold feeds are balanced, it could be a problem with the pressure balancing valve in the mixer.
A new cartridge might be the easiest way to sort it in those circumstances.