Can the fresh water system be used without a filter cartridge? 24 April 2023 06:39 Updated No. The system is blocked without a cartridge. Related articles How long can an installed cartridge be used? Does it make sense to sterilise the water in the tank using UV rays before using the clearliQ travel water filter? How can I tell that the filter needs to be replaced? Will the system also be available for the Mercedes-Benz Sprinter? How does the Grünbeck water filter change my water pressure?