Hi all,
My girlfriend's house has a power shower installed. On Friday night it
made a load bang and then constantly leaked. Then the pump started up
on its own accord. I disconnected it at the consumer unit, and
investigated.

It's a Triton, 4 years old, it's leaking from the pump. Write-off I
reckon. More importantly, the plumber who installed it 4 years ago
connected the cold supply to the MAINS. Illegal obviously - and may
explain why it eventually let go - it is designed apparently for use
with a max head of 10m and goodness knows what pressure the mains is
under.

Anyway, she's now got a problem as to what the replace it with. No way
am I putting a similar power shower in with the current set up.
Plumbing in a new cold feed from the smallish 20 gallon cold water
header tank would be a major hassle, flooboards up, bath out, would the
tank be big enough? Etc.

Electric shower while possible is another big hassle as although we
have cold mains available I would have to run a new 45 amp (?) supply
from one end of the house to the other. I don't fancy that much.

I had a brainwave. Install a single impellor booster pump on the hot
side only, and install a thermostatic mixer valve (cheapy from
Screwfix), run the cold from the mains and she'll then end up with the
equivalent of a fully-fledged power shower!

My question is, can anyone foresee any problems with this idea?
Specifically, bearing in mind the old Triton power shower has run off
the hot tank for years with no problems, will that mean I won't have to
add a Surrey/Essex whatever flange to the tank, as it looks like
cavitation (sucking air) won't be a problem?

I plan to install the pump at the foot of the bath using the
electricity supply from the existing power shower. Any caveats?

Thanks in advance for all your help,
Luke