First of all I fail to see what would cause a blockage in the fresh water system, airlock yes but not a blockage. You can also get airlocks in the pump where it make a noise but doesn’t pump the water.
Check the 12volt system.
Check the pump switch on control panel is not faulty.
Check the power socket for the pump at the outside housing.
If you lift the seat where the water comes in there may be a Whale pressure switch white with wires running to it, which operates the water system as the taps are turned on it senses a pressure change and starts the pump, it may be faulty or no current getting to it (these replaced the need for micro switch taps. The pressure switch is the heart, if that stops so does the water flow.( as well as fuses fault).
Check all fuses, look to see if you have any INLINE fuse holder along the cable runs.
If you are adamant in replacing the water pipes with the shower/wash basin hoses remove from the taps and link the new to old with a straight water pipe connector and clamp with jubilee clips you will need an assistant to feed the pipe as you pull on the old pipe. Hopefully the old pipe work is not clamped under the tray.
bob uk, May 2014