Shower pump making a noise whenever hot water is turned off after use

[Rollerball]

The shower in my bathroom hasn't been used for years but yesterday I checked it out to make sure it was still functional - it was and the shower pump in the airing seems okay (but noisy, as it always was).

However, since that test I'm now often (but not always) finding that after using any hot water tap in the house, as the hot water tap is turned off then the shower pump in the airing cupboard sometimes buzzes for less than a second.

What would cause that, and how can I stop it?

 

[Madrab]

Probably a flow switch. If it hasn't been used in years the components may get a little stale and then things like switch contacts, capacitors etc may get a little noisy. Things like pumps etc like to be used rather than sit idle for years.