Hi folks,

I wonder if someone can offer any advice.

I've just retiled my bathroom, and needed to remove my mixer shower
unit in the process. Having refitted it a few days later, it's behaving
totally differently - beforehand there was a nice gradual change in
temperature as you changed between hot and cold, with no noticeable
change in pressure.

Now it seems to be only doing either hot or cold, with no happy medium.


The pressure also changes - it's difficult to describe but here goes...
Starting from cold, you turn the temperature lever a long way and
suddenly there is a dramatic increase in pressure and the shower goes
(very) hot. If you turn the lever a long way back the other way, the
water suddenly goes ice cold and the pressure drops again. Wherever the
lever is between these two extremes could produce either hot (high
pressure) or cold (low pressure) water from the shower, depending on
which 'extreme' you last visited. Clear as mud, I know. It's b*ggered,
basically.

Our hot water system's unvented, which I sort of assumed meant that
both hot and cold supplies would be working at the same (mains?)
pressure. Anyway, the hot/cold shower feed is just teed off the feed to
the bath taps, which, er, work fine.

Is it possible there is air trapped in the unit - or dirt/scale build
up, in which case should I attempt to completely open the mixer unit up
and give it a good clean? Or is something likely to have gone kaput -
in which case am I likley to be looking at new parts or a new shower?
The only identifiable mark on it is the word "Hydramax".

Cheers.