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? How can I tell that the filter needs to be replaced? Does it make sense to sterilise the water in the tank using UV rays before using the clearliQ travel water filter? How does the Grünbeck water filter change my water pressure? What is the shelf life of a replacement cartridge after purchase?