how do i stop my power shower leaking?

I own a New Team 1000 power shower. when the shower head is hung up the unit leaks, i have taken it apart and it looks like the pump unit is where the water is coming from, it has been tightned but to no avail. I now leave the shower head in the bath and the water leaks through this instead?? It fills the bath by 3 to 4'' in a day so i am keen to sort this wate out. has anyone any ideas as the website for the company is no help at all.
thanks