Power Shower Pump

[nankstar]

I had a twin turbo shower pump fitted last year for a new shower room - seems to work well. Shower room is on 2nd floor, pump is on 1st floor by DHW cylinder. Every now and then the pump seems to start up for a few seconds when nobody is near the shower. I wondered why? I also fitted one of these free water savers to the shower head and have read these can destroy the pump - any suggestions as to why?