Hi - I have installed a Franke pull-out mixer tap (Ta641) on the sink in my lovely new country kitchen. But the water is gravity fed from a spring, the tap has a flow reducer intended for mains water, and I don't know how to remove the reducer. There is a valve which looks like it might house the flow reducer washer called "Restraint Valve Housing" but I don't know if I can just take the whole Restraint Valve Housing out or remove a washer for it, or whether this is any case not the right place to look!  Is there a way I can proceed?

Thanks for the pump idea.  Should have said I get pretty good pressure and flow out of the other taps in the house - laundry etc - so it appears it is flow limitation by the Franke tap.  It's hard to see from the diagram why that happens......