Changing Water supply from direct to tank

I had the same issue on a Jura Giga X8c. From all I read online, it can be changed programmatically, but I didn't find any way of doing this myself. However, I found an easy hardware fix that works does the trick.

I found this diagram, which seems to be for the machine that you are describing, for all matters here however works for the X8c as well. You can see the valve to the tank (X) and the valve to the water line (U). These are both solenoid valves. Only when descaling did my machine open the tank valve and draw liquid from the tank. In any other situation, it only opened the valve to the fixed water line (I confirmed this by actually measuring it).

The hardware fix

• Unplug the machine from the power and open it up. Follow this video for instructions. The oval screw driver came with my iFixit kit.
• Underneath the tank there is an electronic box. This is the box that is responsible for the valve control. On the right hand side of the box there are two vertical connectors, the bottom one having three wire: red, black, brown (from bottom to top). The red wire is +24V, the black and brown wire are the sink wires for the two solenoid valves (more on this in a second). Left of the electronic box you can also see the two lines that go to the steam and the water pump. This is the junction in between the tank (to the right of these two water lines, and the fixed water line (to the left of these two lines).

• Take the electronic box out by taking out the two torx screws on top. You can pull it out.
• Behind the electronic box you will see the tank valve. The tank valve has two wires to it, a red and a brown one. If you trace them it will lead you to that plug on the electronic box. The red wire (+24V) is spliced and also goes to the water line valve

• On the left hand side you will another valve, which is the one for the water line. Here you see again the red wire (coming from the tank valve) as well as a black wire going to that three-wire plug described above.

• What happens when you make a coffee is that the solenoid valve for the fixed water line is opened (voltage applied) while the tank valve is closed.

So my hardware solution to the problem was simply to do the following

1. Disconnect the water line solenoid valve by pulling the plugs off.
2. Solder a wire from the black connector (sink of the fixed water line valve) to the brown wire of the tank valve.
3. Use some tape to seal ensure the water line valve wires can't touch each other or anything else
4. Close the machine back up.

What happens now is that whatever the programming wants it to do, the machine will draw water from the tank since both valve commands go to that valve now and the water line valve is permanently disabled. You will not get a "tank is empty" warning since the machine simply doesn't know it's connected to the tank, but that's a issue I am more than willing to take.

I hope this helps, might be a bit late for you (or maybe not), but I came across this question while looking for the same answer myself and figured the next person might find this helpful. Let me know if anything is unclear!