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