The Mira 88 mixer shower we have was fitted when the house was built in 1990. It is cold tank/hot tank supplied. Apart from never having had a strong flow (3.5lt/m!!) it has always worked ok until now.
Last year this problem came and went away, not sure if I cured it or if it righted itself. But now it is back again. With the mixer knob turned to Cold it runs fine. With it turned to Hot it runs fine. When adjusted to "normal" showering temp it is fine, all with the shower head held at waist height. However, lower the showerhead and the water goes cold, raise it above head height and it runs scalding hot! Ouch! You have to lower the showerhead back down to knee height to cool the water flow down again.
It does this with no other taps in the house being used and all the taps have a good water pressure/feed. I have tried "sealing" the showerhead end with it held low and then raising it held high and down again many times, also done this with it set at hot, cold and "normal" temps in the thought of it being an airlock somewhere and trying to force the water back up the line forcing the air out if there is any.
It still runs hot when held high and cold when held low :-(
Any help will be gratefully received. Thanks