I've recently replaced my hot water system for a heatbank based
system, so I've now got mains pressure water everywhere.

As the mains in our house has a static pressure of around 7 bar, I
fitted a pressure reducing valve on the rising main, which I've set to
around 2 bar.

Since this change my Mira thermostatic shower, which is around a year
old, makes a horrible whining sound when it's running. I can stop it
for a few seconds by adjusting the flow, but it soon comes back. I
also put a flow restrictor in the flexible pipe between the shower and
the head as it could take your skin off on full whack, but this didn't
make any difference to the noise.

Any ideas on what would be causing this? Should I contact Mira and try
to get them to replace it?

Thanks,
Dave.