What you'll need:
2.5mm allen key
3mm allen key
13mm wrench
19mm wrench or socket
Scotch-Brite pad
Cafiza/espresso cleaning solution
PTFE tape
NOTE: Drain the machine's boilers before attempting this procedure; then unplug the machine and allow it to cool down.
1. Start by removing the panels from the machine.
2. Locate the fill probe, and disconnect the electrical lead the top (red wire).
3. Use the 13mm wrench to loosen the top nut portion of the probe connection.(You may need to remove the surrounding components to have room to work.)
4. Use a 19mm wrench or deep socket to unscrew the bottom nut and remove the whole fill probe assembly.
5. Use a scouring pad or wire brush and a mixture of hot water and Cafiza to scrub off any scale/mineral buildup. If your paper washer looks like the one pictured below, you will need to clean it off and wrap the threads with some PTFE tape to create a seal.
6. Reinsert the probe or reinstall the whole probe assembly into the boiler and reattach the electrical lead.
7. Plug the machine back in and power it on to test for leaks before reinstalling the side panels.