Question

my cold water truma pistol pump runs all the time when switched on, does the pump need calibrating and how do you do it?

Answer

This is not related to the pump itself. If the pump is controlled by microswitches in each tap then it is possible that one of the switches is 'closed' at all times causing the pump to run continuously. You will need to identify the faulty switch and replace.
If the pump is controlled by a pressure switch then it may simply be a case of making an adjustment to the switch. I will need to know the model of pump and pressure switch that is fitted.