The gasket seals the water inlet into the flow meter. It is seated below the water tank outlet. When the machine leaks from water tank, please check this gasket. Ensure the water tank is seated properly. Older Jura machines used the Black gasket. Red gasket is better than Black.
How to Check Leaking Jura Water Tank
Leaking Water Tank: Leak from water tank could be due to worn out gasket. Remove the filled water tank from the machine and place it on a dry surface away from the machine. If there is leakage than there is issue with the water tank.
Worn Out Gasket: After testing the above, it the water tank leaks, then replace the red gasket. In either case, the leak could result in FILL SYSTEM error.