Issues with a water pump on bath?

[mattman]

Hi - not sure what is going on with our water system.
About 6mths ago we refitted the bathroom and had to fit a pump to get the new taps to fill the bath in a resonable time.

Every now and then when I turn the kitchen tap off the bath pump runs a couple of pulses - any reason why?

Also, the bath fills fine, but as it gets near full the pum struggles and sometimes turns off as if the water isn't getting through - it runs fine and strong during the first fill so don't think its a restriction in the pipes?
Its a standard 2 floor house, water tank in the roof on a gravity fed system.

any ideas before I call the plumber out

[Arthur Jackson]

The flow switch is picking up a vibrarion in the water. You could fit a non-return valve in the feed in to stop this. It also sounds like it's emptying the tank. This is really bad for pumps they shouldn't pump air...