The shower is about 6 years old and has always worked perfectly until this last week. There has been a sudden loss of volume on the hot side, so when the thermostat is turn to full heat, the water volume is much lower than it used to be. Is this a fault in the hot side of the pump, or, in the thermostat at the mixer, or somewhere else? Are these problems when found repairable with spares or only by replacement of the whole unit? Thanks for any experienced reply.