POWER SHOWER PUMP TURNS ITSELF ON

[matt632]

I have installed a power shower pump into the hot and cold feed of a gravity fed mixer shower. The mixer unit is suitable for this.
Initially the pump worker fine, but recently (6 months on) the pump has begun to activate for a short period (1 sec) when I turn any hot water tap off in the house. This seems to be getting worse.

Does anybody know why this may be happening?

 

[ArtfulBodger]

Does it have it's own dedicated water supply? is it negative head?

 

[matt632]

No, it is a positive head supplied off of the hot and cold header tanks in the loft. I think on further research that air in the pipe between the pump and the shower may be causing the problem, does that sound plausible? It is quite a long run and has an obvious high point that could trap air.