Surface mounted mixer shower starts hot then cools down.Decided to dismantle having removed the temp control and flow control i finally managed to remove the internal valve. This looked scaled up but ok took photo so could go off and get replacement. I then re-assembled it all in reverse order how ever i can't now turn the shower off using the hand controls. I have looked at the whole assemble and there is no obvious markings to say which way round the valve should go. I'm replacing the whole unit but would like to know why it would'nt turn off.