There is a short pipe attached to it to which the shower hose is connected. The integral nut on the short pipe is too big to come out through the outer case.
So far as I can see the only way is to remove the unit from the wall and supply pipes and remove every single component.
Great design, Triton (not) :(
Derek Roberts, July 2009
remove the two screws holding it in the bottom of the pump then it will pull out.