Power shower

[Kazal]

A short while after we had a power shower fitted (about 4 years ago!!) we noticed the shower head had a red residue on it which is very difficult to remove (in fact we cannot remove all of it). After it has been cleaned it comes back shortly afterwards, it also appears on the shower curtain. We asked the guy who fitted it but he just scratched his head.Recently we have been told that it's bad news.Any suggestions please.

[Hermia]

Is it a deep pink colour? If so, it is probably this stuff: http://en.wikipedia.org/wiki/Serratia_marcesce ns

I have it in my bathroom. The only way to get rid of it is to use bleach and leave it on a while (I use a bleach spray on the tiles etc). It has a tendency to come back though.