I have a watermill shower pump which is linked to upstairs taps and upstairs mixer shower. The pump manages the hot and cold water and is enabled when either tap is turned. The taps work great and the pump turns on and the then off when the tap turned off. When we use the shower the pump goes on and off. When off there is still water coming out of the shower and then 4 seconds later (not timed! ) the pump comes on again. To have a constant shower I have to turn on the cold tap in the bathroom to have a constant shower.

Hope someone can help.

I a good DIY er but not an expert !